* So I have recoded an alternative command called asim
* This command allow subsequent simulate commands to be run, saving the old data in memory appended to the current data.
cap program drop asim
program define asim
* This will allow the user to specify a value to assign to the asim variable which is generated after the simulation is run.
gettoken before after : 0 , parse(":")
local simulation = subinstr("`after'", ":", "", 1)
cap save `tempsave'
* This will append in the new simulation data to the old data set.
gen asim = "`before'"
cap append using `tempsave'
* Let's write a nice little program that we would like to simulate.
cap program drop simCLT
program define simCLT
set obs `1'
* 1 is defined as the first argument of the program sim
* Let's say we would like to see how many observations we need for the central limit theorem (CLT) to hold for a bernoulli distribution.
gen x = rbinomial(1,.25)
* So let's see first how the simulate command works initially.
simulate, rep(200): simCLT 100
* The simulate command will automatically save the returns from the sum command as variables (at least in version 12)
* But instead let's try our new command!
* Clear out the old results
asim 0100: simulate, rep(200): simCLT 100
asim 0200: simulate, rep(200): simCLT 200
* Looks good!
asim 0400: simulate, rep(200): simCLT 400
asim 1000: simulate, rep(200): simCLT 1000
asim 10000: simulate, rep(200): simCLT 1000
asim 100000: simulate, rep(200): simCLT 1000
* Standardize the individual means of each run so as to more easily compare them with each other.
bysort asim: egen sd_mean = sd(mean)
bysort asim: egen mean_mean = mean(mean)
gen std_mean = (mean-mean_mean)/sd_mean
hist std_mean, kden by(asim)
* We can see that this generate data is much easier to use than that using many different variables.
* It looks a little funny with some of the numbers having zeros in front. However, this was the best way to do it given that the asim variable is text.
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