HARK.utilities¶
General purpose / miscellaneous functions. Includes functions to approximate continuous distributions with discrete ones, utility functions (and their derivatives), manipulation of discrete distributions, and basic plotting tools.
Functions
CARAutility (c, alpha) 
Evaluates constant absolute risk aversion (CARA) utility of consumption c given risk aversion parameter alpha. 
CARAutilityP (c, alpha) 
Evaluates constant absolute risk aversion (CARA) marginal utility of consumption c given risk aversion parameter alpha. 
CARAutilityPP (c, alpha) 
Evaluates constant absolute risk aversion (CARA) marginal marginal utility of consumption c given risk aversion parameter alpha. 
CARAutilityPPP (c, alpha) 
Evaluates constant absolute risk aversion (CARA) marginal marginal marginal utility of consumption c given risk aversion parameter alpha. 
CARAutilityP_inv (u, alpha) 
Evaluates the inverse of constant absolute risk aversion (CARA) marginal utility function at marginal utility uP given risk aversion parameter alpha. 
CARAutility_inv (u, alpha) 
Evaluates inverse of constant absolute risk aversion (CARA) utility function at utility level u given risk aversion parameter alpha. 
CARAutility_invP (u, alpha) 
Evaluates the derivative of inverse of constant absolute risk aversion (CARA) utility function at utility level u given risk aversion parameter alpha. 
CRRAutility (c, gam) 
Evaluates constant relative risk aversion (CRRA) utility of consumption c given risk aversion parameter gam. 
CRRAutilityP (c, gam) 
Evaluates constant relative risk aversion (CRRA) marginal utility of consumption c given risk aversion parameter gam. 
CRRAutilityPP (c, gam) 
Evaluates constant relative risk aversion (CRRA) marginal marginal utility of consumption c given risk aversion parameter gam. 
CRRAutilityPPP (c, gam) 
Evaluates constant relative risk aversion (CRRA) marginal marginal marginal utility of consumption c given risk aversion parameter gam. 
CRRAutilityPPPP (c, gam) 
Evaluates constant relative risk aversion (CRRA) marginal marginal marginal marginal utility of consumption c given risk aversion parameter gam. 
CRRAutilityP_inv (uP, gam) 
Evaluates the inverse of the CRRA marginal utility function (with risk aversion parameter gam) at a given marginal utility level uP. 
CRRAutilityP_invP (uP, gam) 
Evaluates the derivative of the inverse of the CRRA marginal utility function (with risk aversion parameter gam) at a given marginal utility level uP. 
CRRAutility_inv (u, gam) 
Evaluates the inverse of the CRRA utility function (with risk aversion para meter gam) at a given utility level u. 
CRRAutility_invP (u, gam) 
Evaluates the derivative of the inverse of the CRRA utility function (with risk aversion parameter gam) at a given utility level u. 
addDiscreteOutcome (distribution, x, p[, sort]) 
Adds a discrete outcome of x with probability p to an existing distribution, holding constant the relative probabilities of other outcomes. 
addDiscreteOutcomeConstantMean (distribution, …) 
Adds a discrete outcome of x with probability p to an existing distribution, holding constant the relative probabilities of other outcomes and overall mean. 
approxBeta (N[, a, b]) 
Calculate a discrete approximation to the beta distribution. 
approxLognormal (N[, mu, sigma, tail_N, …]) 
Construct a discrete approximation to a lognormal distribution with underlying normal distribution N(mu,sigma). 
approxLognormalGaussHermite (N[, mu, sigma]) 

approxMeanOneLognormal (N[, sigma]) 
Calculate a discrete approximation to a mean one lognormal distribution. 
approxNormal (N[, mu, sigma]) 

approxUniform (N[, bot, top]) 
Makes a discrete approximation to a uniform distribution, given its bottom and top limits and number of points. 
calcLognormalStyleParsFromNormalPars (…) 

calcNormalStyleParsFromLognormalPars (…) 

calcSubpopAvg (data, reference, cutoffs[, …]) 
Calculates the average of (weighted) data between cutoff percentiles of a reference variable. 
calcWeightedAvg (data, weights) 
Generates a weighted average of simulated data. 
combineIndepDstns (\*distributions) 
Given n lists (or tuples) whose elements represent n independent, discrete probability spaces (probabilities and values), construct a joint pmf over all combinations of these independent points. 
epanechnikovKernel (x, ref_x[, h]) 
The Epanechnikov kernel. 
getArgNames (function) 
Returns a list of strings naming all of the arguments for the passed function. 
getLorenzShares (data[, weights, …]) 
Calculates the Lorenz curve at the requested percentiles of (weighted) data. 
getPercentiles (data[, weights, percentiles, …]) 
Calculates the requested percentiles of (weighted) data. 
kernelRegression (x, y[, bot, top, N, h]) 
Performs a nonparametric NadarayaWatson 1D kernel regression on given data with optionally specified range, number of points, and kernel bandwidth. 
main () 

makeGridExpMult (ming, maxg, ng[, timestonest]) 
Make a multiexponentially spaced grid. 
makeMarkovApproxToNormal (x_grid, mu, sigma) 
Creates an approximation to a normal distribution with mean mu and standard deviation sigma, returning a stochastic vector called p_vec, corresponding to values in x_grid. 
makeMarkovApproxToNormalByMonteCarlo (x_grid, …) 
Creates an approximation to a normal distribution with mean mu and standard deviation sigma, by Monte Carlo. 
makeTauchenAR1 (N[, sigma, rho, bound]) 
Function to return a discretized version of an AR1 process. 
memoize (obj) 
A decorator to (potentially) make functions more efficient. 
plotFuncs (functions, bottom, top[, N, …]) 
Plots 1D function(s) over a given range. 
plotFuncsDer (functions, bottom, top[, N, …]) 
Plots the first derivative of 1D function(s) over a given range. 
Classes
NullFunc 
A trivial class that acts as a placeholder “do nothing” function. 

HARK.utilities.
CARAutility
(c, alpha)¶ Evaluates constant absolute risk aversion (CARA) utility of consumption c given risk aversion parameter alpha.
Parameters:  c: float
Consumption value
 alpha: float
Risk aversion
Returns:  (unnamed): float
Utility

HARK.utilities.
CARAutilityP
(c, alpha)¶ Evaluates constant absolute risk aversion (CARA) marginal utility of consumption c given risk aversion parameter alpha.
Parameters:  c: float
Consumption value
 alpha: float
Risk aversion
Returns:  (unnamed): float
Marginal utility

HARK.utilities.
CARAutilityPP
(c, alpha)¶ Evaluates constant absolute risk aversion (CARA) marginal marginal utility of consumption c given risk aversion parameter alpha.
Parameters:  c: float
Consumption value
 alpha: float
Risk aversion
Returns:  (unnamed): float
Marginal marginal utility

HARK.utilities.
CARAutilityPPP
(c, alpha)¶ Evaluates constant absolute risk aversion (CARA) marginal marginal marginal utility of consumption c given risk aversion parameter alpha.
Parameters:  c: float
Consumption value
 alpha: float
Risk aversion
Returns:  (unnamed): float
Marginal marginal marginal utility

HARK.utilities.
CARAutilityP_inv
(u, alpha)¶ Evaluates the inverse of constant absolute risk aversion (CARA) marginal utility function at marginal utility uP given risk aversion parameter alpha.
Parameters:  u: float
Utility value
 alpha: float
Risk aversion
Returns:  (unnamed): float
Consumption value corresponding to uP

HARK.utilities.
CARAutility_inv
(u, alpha)¶ Evaluates inverse of constant absolute risk aversion (CARA) utility function at utility level u given risk aversion parameter alpha.
Parameters:  u: float
Utility value
 alpha: float
Risk aversion
Returns:  (unnamed): float
Consumption value corresponding to u

HARK.utilities.
CARAutility_invP
(u, alpha)¶ Evaluates the derivative of inverse of constant absolute risk aversion (CARA) utility function at utility level u given risk aversion parameter alpha.
Parameters:  u: float
Utility value
 alpha: float
Risk aversion
Returns:  (unnamed): float
Marginal onsumption value corresponding to u

HARK.utilities.
CRRAutility
(c, gam)¶ Evaluates constant relative risk aversion (CRRA) utility of consumption c given risk aversion parameter gam.
Parameters:  c : float
Consumption value
 gam : float
Risk aversion
Returns:  (unnamed) : float
Utility

HARK.utilities.
CRRAutilityP
(c, gam)¶ Evaluates constant relative risk aversion (CRRA) marginal utility of consumption c given risk aversion parameter gam.
Parameters:  c : float
Consumption value
 gam : float
Risk aversion
Returns:  (unnamed) : float
Marginal utility

HARK.utilities.
CRRAutilityPP
(c, gam)¶ Evaluates constant relative risk aversion (CRRA) marginal marginal utility of consumption c given risk aversion parameter gam.
Parameters:  c : float
Consumption value
 gam : float
Risk aversion
Returns:  (unnamed) : float
Marginal marginal utility

HARK.utilities.
CRRAutilityPPP
(c, gam)¶ Evaluates constant relative risk aversion (CRRA) marginal marginal marginal utility of consumption c given risk aversion parameter gam.
Parameters:  c : float
Consumption value
 gam : float
Risk aversion
Returns:  (unnamed) : float
Marginal marginal marginal utility

HARK.utilities.
CRRAutilityPPPP
(c, gam)¶ Evaluates constant relative risk aversion (CRRA) marginal marginal marginal marginal utility of consumption c given risk aversion parameter gam.
Parameters:  c : float
Consumption value
 gam : float
Risk aversion
Returns:  (unnamed) : float
Marginal marginal marginal marginal utility

HARK.utilities.
CRRAutilityP_inv
(uP, gam)¶ Evaluates the inverse of the CRRA marginal utility function (with risk aversion parameter gam) at a given marginal utility level uP.
Parameters:  uP : float
Marginal utility value
 gam : float
Risk aversion
Returns:  (unnamed) : float
Consumption corresponding to given marginal utility value.

HARK.utilities.
CRRAutilityP_invP
(uP, gam)¶ Evaluates the derivative of the inverse of the CRRA marginal utility function (with risk aversion parameter gam) at a given marginal utility level uP.
Parameters:  uP : float
Marginal utility value
 gam : float
Risk aversion
Returns:  (unnamed) : float
Marginal consumption corresponding to given marginal utility value

HARK.utilities.
CRRAutility_inv
(u, gam)¶ Evaluates the inverse of the CRRA utility function (with risk aversion para meter gam) at a given utility level u.
Parameters:  u : float
Utility value
 gam : float
Risk aversion
Returns:  (unnamed) : float
Consumption corresponding to given utility value

HARK.utilities.
CRRAutility_invP
(u, gam)¶ Evaluates the derivative of the inverse of the CRRA utility function (with risk aversion parameter gam) at a given utility level u.
Parameters:  u : float
Utility value
 gam : float
Risk aversion
Returns:  (unnamed) : float
Marginal consumption corresponding to given utility value

class
HARK.utilities.
NullFunc
¶ A trivial class that acts as a placeholder “do nothing” function.
Methods
__call__
(self, \*args)Returns meaningless output no matter what the input(s) is. distance
(self, other)Trivial distance metric that only cares whether the other object is also an instance of NullFunc. 
distance
(self, other)¶ Trivial distance metric that only cares whether the other object is also an instance of NullFunc. Intentionally does not inherit from HARKobject as this might create dependency problems.
Parameters:  other : any
Any object for comparison to this instance of NullFunc.
Returns:  (unnamed) : float
The distance between self and other. Returns 0 if other is also a NullFunc; otherwise returns an arbitrary high number.


HARK.utilities.
addDiscreteOutcome
(distribution, x, p, sort=False)¶ Adds a discrete outcome of x with probability p to an existing distribution, holding constant the relative probabilities of other outcomes.
Parameters:  distribution : [np.array]
Two element list containing a list of probabilities and a list of outcomes.
 x : float
The new value to be added to the distribution.
 p : float
The probability of the discrete outcome x occuring.
Returns:  X : np.array
Discrete points for discrete probability mass function.
 pmf : np.array
Probability associated with each point in X.
 Written by Matthew N. White
 Latest update: 11 December 2015

HARK.utilities.
addDiscreteOutcomeConstantMean
(distribution, x, p, sort=False)¶ Adds a discrete outcome of x with probability p to an existing distribution, holding constant the relative probabilities of other outcomes and overall mean.
Parameters:  distribution : [np.array]
Two element list containing a list of probabilities and a list of outcomes.
 x : float
The new value to be added to the distribution.
 p : float
The probability of the discrete outcome x occuring.
 sort: bool
Whether or not to sort X before returning it
Returns:  X : np.array
Discrete points for discrete probability mass function.
 pmf : np.array
Probability associated with each point in X.
 Written by Matthew N. White
 Latest update: 08 December 2015 by David Low

HARK.utilities.
approxBeta
(N, a=1.0, b=1.0)¶ Calculate a discrete approximation to the beta distribution. May be quite slow, as it uses a rudimentary numeric integration method to generate the discrete approximation.
Parameters:  N : int
Size of discrete space vector to be returned.
 a : float
First shape parameter (sometimes called alpha).
 b : float
Second shape parameter (sometimes called beta).
Returns:  X : np.array
Discrete points for discrete probability mass function.
 pmf : np.array
Probability associated with each point in X.

HARK.utilities.
approxLognormal
(N, mu=0.0, sigma=1.0, tail_N=0, tail_bound=[0.02, 0.98], tail_order=2.718281828459045)¶ Construct a discrete approximation to a lognormal distribution with underlying normal distribution N(mu,sigma). Makes an equiprobable distribution by default, but user can optionally request augmented tails with exponentially sized point masses. This can improve solution accuracy in some models.
Parameters:  N: int
Number of discrete points in the “main part” of the approximation.
 mu: float
Mean of underlying normal distribution.
 sigma: float
Standard deviation of underlying normal distribution.
 tail_N: int
Number of points in each “tail part” of the approximation; 0 = no tail.
 tail_bound: [float]
CDF boundaries of the tails vs main portion; tail_bound[0] is the lower tail bound, tail_bound[1] is the upper tail bound. Inoperative when tail_N = 0. Can make “one tailed” approximations with 0.0 or 1.0.
 tail_order: float
Factor by which consecutive point masses in a “tail part” differ in probability. Should be >= 1 for sensible spacing.
Returns:  pmf: np.ndarray
Probabilities for discrete probability mass function.
 X: np.ndarray
Discrete values in probability mass function.
 Written by Luca Gerotto
 Based on Matab function “setup_workspace.m,” from Chris Carroll’s
[Solution Methods for Microeconomic Dynamic Optimization Problems] (http://www.econ2.jhu.edu/people/ccarroll/solvingmicrodsops/) toolkit.
 Latest update: 11 February 2017 by Matthew N. White

HARK.utilities.
approxMeanOneLognormal
(N, sigma=1.0, **kwargs)¶ Calculate a discrete approximation to a mean one lognormal distribution. Based on function approxLognormal; see that function’s documentation for further notes.
Parameters:  N : int
Size of discrete space vector to be returned.
 sigma : float
standard deviation associated with underlying normal probability distribution.
Returns:  X : np.array
Discrete points for discrete probability mass function.
 pmf : np.array
Probability associated with each point in X.
 Written by Nathan M. Palmer
 Based on Matab function “setup_shocks.m,” from Chris Carroll’s
[Solution Methods for Microeconomic Dynamic Optimization Problems] (http://www.econ2.jhu.edu/people/ccarroll/solvingmicrodsops/) toolkit.
 Latest update: 01 May 2015

HARK.utilities.
approxUniform
(N, bot=0.0, top=1.0)¶ Makes a discrete approximation to a uniform distribution, given its bottom and top limits and number of points.
Parameters:  N : int
The number of points in the discrete approximation
 bot : float
The bottom of the uniform distribution
 top : float
The top of the uniform distribution
Returns:  (unnamed) : np.array
An equiprobable discrete approximation to the uniform distribution.

HARK.utilities.
calcSubpopAvg
(data, reference, cutoffs, weights=None)¶ Calculates the average of (weighted) data between cutoff percentiles of a reference variable.
Parameters:  data : numpy.array
A 1D array of float data.
 reference : numpy.array
A 1D array of float data of the same length as data.
 cutoffs : [(float,float)]
A list of doubles with the lower and upper percentile bounds (should be in [0,1]).
 weights : numpy.array
A weighting vector for the data.
Returns:  slice_avg
The (weighted) average of data that falls within the cutoff percentiles of reference.

HARK.utilities.
calcWeightedAvg
(data, weights)¶ Generates a weighted average of simulated data. The Nth row of data is averaged and then weighted by the Nth element of weights in an aggregate average.
Parameters:  data : numpy.array
An array of data with N rows of J floats
 weights : numpy.array
A length N array of weights for the N rows of data.
Returns:  weighted_sum : float
The weighted sum of the data.

HARK.utilities.
combineIndepDstns
(*distributions)¶ Given n lists (or tuples) whose elements represent n independent, discrete probability spaces (probabilities and values), construct a joint pmf over all combinations of these independent points. Can take multivariate discrete distributions as inputs.
Parameters:  distributions : [np.array]
Arbitrary number of distributions (pmfs). Each pmf is a list or tuple. For each pmf, the first vector is probabilities and all subsequent vectors are values. For each pmf, this should be true: len(X_pmf[0]) == len(X_pmf[j]) for j in range(1,len(distributions))
Returns:  List of arrays, consisting of:
 P_out: np.array
Probability associated with each point in X_out.
 X_out: np.array (as many as in *distributions)
Discrete points for the joint discrete probability mass function.
 Written by Nathan Palmer
 Latest update: 5 July August 2017 by Matthew N White

HARK.utilities.
epanechnikovKernel
(x, ref_x, h=1.0)¶ The Epanechnikov kernel.
Parameters:  x : np.array
Values at which to evaluate the kernel
 x_ref : float
The reference point
 h : float
Kernel bandwidth
Returns:  out : np.array
Kernel values at each value of x

HARK.utilities.
getArgNames
(function)¶ Returns a list of strings naming all of the arguments for the passed function.
Parameters:  function : function
A function whose argument names are wanted.
Returns:  argNames : [string]
The names of the arguments of function.
Calculates the Lorenz curve at the requested percentiles of (weighted) data. Median by default.
Parameters:  data : numpy.array
A 1D array of float data.
 weights : numpy.array
A weighting vector for the data.
 percentiles : [float]
A list of percentiles to calculate for the data. Each element should be in (0,1).
 presorted : boolean
Indicator for whether data has already been sorted.
Returns:  lorenz_out : numpy.array
The requested Lorenz curve points of the data.

HARK.utilities.
getPercentiles
(data, weights=None, percentiles=[0.5], presorted=False)¶ Calculates the requested percentiles of (weighted) data. Median by default.
Parameters:  data : numpy.array
A 1D array of float data.
 weights : np.array
A weighting vector for the data.
 percentiles : [float]
A list of percentiles to calculate for the data. Each element should be in (0,1).
 presorted : boolean
Indicator for whether data has already been sorted.
Returns:  pctl_out : numpy.array
The requested percentiles of the data.

HARK.utilities.
kernelRegression
(x, y, bot=None, top=None, N=500, h=None)¶ Performs a nonparametric NadarayaWatson 1D kernel regression on given data with optionally specified range, number of points, and kernel bandwidth.
Parameters:  x : np.array
The independent variable in the kernel regression.
 y : np.array
The dependent variable in the kernel regression.
 bot : float
Minimum value of interest in the regression; defaults to min(x).
 top : float
Maximum value of interest in the regression; defaults to max(y).
 N : int
Number of points to compute.
 h : float
The bandwidth of the (Epanechnikov) kernel. Todo: GENERALIZE.
Returns:  regression : LinearInterp
A piecewise locally linear kernel regression: y = f(x).

HARK.utilities.
makeGridExpMult
(ming, maxg, ng, timestonest=20)¶ Make a multiexponentially spaced grid.
Parameters:  ming : float
Minimum value of the grid
 maxg : float
Maximum value of the grid
 ng : int
The number of grid points
 timestonest : int
the number of times to nest the exponentiation
Returns:  points : np.array
A multiexponentially spaced grid
 Original Matab code can be found in Chris Carroll’s
 [Solution Methods for Microeconomic Dynamic Optimization Problems]
 (http://www.econ2.jhu.edu/people/ccarroll/solvingmicrodsops/) toolkit.
 Latest update: 01 May 2015

HARK.utilities.
makeMarkovApproxToNormal
(x_grid, mu, sigma, K=351, bound=3.5)¶ Creates an approximation to a normal distribution with mean mu and standard deviation sigma, returning a stochastic vector called p_vec, corresponding to values in x_grid. If a RV is distributed x~N(mu,sigma), then the expectation of a continuous function f() is E[f(x)] = numpy.dot(p_vec,f(x_grid)).
Parameters:  x_grid: numpy.array
A sorted 1D array of floats representing discrete values that a normally distributed RV could take on.
 mu: float
Mean of the normal distribution to be approximated.
 sigma: float
Standard deviation of the normal distribution to be approximated.
 K: int
Number of points in the normal distribution to sample.
 bound: float
Truncation bound of the normal distribution, as +/ bound*sigma.
Returns:  p_vec: numpy.array
A stochastic vector with probability weights for each x in x_grid.

HARK.utilities.
makeMarkovApproxToNormalByMonteCarlo
(x_grid, mu, sigma, N_draws=10000)¶ Creates an approximation to a normal distribution with mean mu and standard deviation sigma, by Monte Carlo. Returns a stochastic vector called p_vec, corresponding to values in x_grid. If a RV is distributed x~N(mu,sigma), then the expectation of a continuous function f() is E[f(x)] = numpy.dot(p_vec,f(x_grid)).
Parameters:  x_grid: numpy.array
A sorted 1D array of floats representing discrete values that a normally distributed RV could take on.
 mu: float
Mean of the normal distribution to be approximated.
 sigma: float
Standard deviation of the normal distribution to be approximated.
 N_draws: int
Number of draws to use in Monte Carlo.
Returns:  p_vec: numpy.array
A stochastic vector with probability weights for each x in x_grid.

HARK.utilities.
makeTauchenAR1
(N, sigma=1.0, rho=0.9, bound=3.0)¶ Function to return a discretized version of an AR1 process. See http://www.fperri.net/TEACHING/macrotheory08/numerical.pdf for details
Parameters:  N: int
Size of discretized grid
 sigma: float
Standard deviation of the error term
 rho: float
AR1 coefficient
 bound: float
The highest (lowest) grid point will be bound (bound) multiplied by the unconditional standard deviation of the process
Returns:  y: np.array
Grid points on which the discretized process takes values
 trans_matrix: np.array
Markov transition array for the discretized process
 Written by Edmund S. Crawley
 Latest update: 27 October 2017

HARK.utilities.
memoize
(obj)¶ A decorator to (potentially) make functions more efficient.
With this decorator, functions will “remember” if they have been evaluated with given inputs before. If they have, they will “remember” the outputs that have already been calculated for those inputs, rather than calculating them again.

HARK.utilities.
plotFuncs
(functions, bottom, top, N=1000, legend_kwds=None)¶ Plots 1D function(s) over a given range.
Parameters:  functions : [function] or function
A single function, or a list of functions, to be plotted.
 bottom : float
The lower limit of the domain to be plotted.
 top : float
The upper limit of the domain to be plotted.
 N : int
Number of points in the domain to evaluate.
 legend_kwds: None, or dictionary
If not None, the keyword dictionary to pass to plt.legend
Returns:  none

HARK.utilities.
plotFuncsDer
(functions, bottom, top, N=1000, legend_kwds=None)¶ Plots the first derivative of 1D function(s) over a given range.
Parameters:  function : function
A function or list of functions, the derivatives of which are to be plotted.
 bottom : float
The lower limit of the domain to be plotted.
 top : float
The upper limit of the domain to be plotted.
 N : int
Number of points in the domain to evaluate.
 legend_kwds: None, or dictionary
If not None, the keyword dictionary to pass to plt.legend
Returns:  none