topic Re: How to calculate the difference between two identical tables ? in Discussions

How to calculate the difference between two identical tables ?

SamplingHamster — Mon, 26 May 2025 07:51:27 GMT

Hi,

I have two identical tables of test results from two different times.

Is there a simple function that can calculate the difference for each case?

Re: How to calculate the difference between two identical tables ?

jthi — Mon, 26 May 2025 08:37:11 GMT

I'm not sure what the identical means here (in identical tables the difference would be 0?). Do you have same column names? Where should the result be stored? What is "each case", difference of columns?

Re: How to calculate the difference between two identical tables ?

SamplingHamster — Mon, 26 May 2025 09:05:27 GMT

Hi,

Thanks for you reply.

Labels of Colums and Rows are the same. Values are differents. I want to calculate the drift of each cell (sorry not each case).

Re: How to calculate the difference between two identical tables ?

jthi — Mon, 26 May 2025 09:38:47 GMT

Not sure where the results should be calculated, so I will demonstrate fairly simple process which will create new table with the result

Join tables together using By Row Number

Pick columns in pairs and create the formulas

And you should end up with the result columns as formulas

Re: How to calculate the difference between two identical tables ?

Craige_Hales — Mon, 26 May 2025 11:56:31 GMT

If the table is all numeric, you could use data table subscripting to make a pair of matrices and subtract them, then write them back to a new table.
With a little more work, you could do the same thing by choosing just the numeric columns.

Re: How to calculate the difference between two identical tables ?

jthi — Mon, 26 May 2025 12:36:31 GMT

And this would be the idea using data table subscripting and creating a new table

Names Default To Here(1);

dt = Open("$SAMPLE_DATA/Big Class.jmp");
dt2 = Open("$SAMPLE_DATA/Big Class Families.jmp");
dt2 << Sort(By(:sports),Replace Table,Order(Ascending),Copy formula(0)); // demo purposes

If(N Rows(dt) != N Rows(dt),
	Throw("Rows do not match");
);

cont_cols1 = dt << Get Column Names(Continuous, "String");
cont_cols2 = dt2 << Get Column Names(Continuous, "String");

If(cont_cols1 != cont_cols2,
	Throw("Columns do not match");
);

res = dt[0, cont_cols1] - dt2[0, cont_cols2];

dt_res = As Table(res);
For Each({colname, idx}, cont_cols1,
	Column(dt_res, idx) << Set Name(colname);
);

Re: How to calculate the difference between two identical tables ?

txnelson — Mon, 26 May 2025 12:43:47 GMT

Here is a simple script that will take 2 identical all numeric tables....identical in column names and number of rows, and create a new table that is the difference between the 2 tables

names default to here(1);
dt1 = data table("name of first table");
dt2 = data table("name of second table");
// Create a new table from one of the 2 tables
dt3 = dt1 << subset( selected rows(0), selected columns(0));
// Replace cell values in the third data table with the 
// differences between table 1 and table 2
dt3[0,0] = dt1[0,0]-dt2[0,0];

Re: How to calculate the difference between two identical tables ?

SamplingHamster — Tue, 27 May 2025 11:26:58 GMT

Thank you for your help. It works.