Random Sampling with Replacement

wendytseng

Is it possible to do this?  It does not appear the Tables --> Subset function allows for this.  

 

I recognize that you can get Bootstrap estimates in various parts of the JMP Pro platform but I am wondering specifically about generating data tables.

 

Thank you!

brady_brady

Hi Wendy,

 

Not sure whether your customer is willing to script, but the idea can readily be extended to stratify wrt a categorical variable. The short script below does this for the Car Physical Data dataset and the "Type" column. 1000 rows are requested, where the original table has 116. Note that 1002 rows are returned, due to rounding up to the nearest integer the sample size of each category.

 

This isn't the fastest way to do this, but it is relatively straightforward to understand. Perhaps your customer will be able to script what they want if you talk them through this?

 

Cheers,

Brady

 

Names Default To Here( 1 );

dt = Open( "$Sample_Data\Car Physical Data.jmp" );

stratCol = Column( dt, "Type" );

nSample = 1000;

//determine the (over)sampling ratio
sRatio = nSample / N Row( dt );

//get a list of the stratification column's values
categories = ((Associative Array( stratCol << get values ) << get keys));

// initialize the master row matrix
rowMat = [];

//For each category
For( i = 1, i <= N Items( categories ), i++,

	// Get the table rows belonging to this category
	catRows = dt << getrowswhere( dt:stratCol == categories[i] );
	
	// Determine how many rows belong to this category
	catN = N Items( catRows );
	
	// Oversample these row values by the specified ratio, and append them to the master row list
	rowMat |/= catRows[As List( J( Ceiling( catN * sRatio ), 1, Random Integer( 1, catN ) ) )];
);

// Subset the data table, using the final master row list
dt << subset( rows( As List( rowMat ) ) );