topic Re: get rows where returning empty matrix in Discussions

get rows where returning empty matrix

h_lazar — Sat, 14 Mar 2015 02:40:25 GMT

I have a data table that I am trying to manipulate. I am using get rows where function to find where the first column equals a string, let's call it "aaa". When I use the software to do this, it works fine and two rows are selected, row 1 and row 2240. When I try to script this, the result is an empty matrix.

Here is the script I am using:


Names Default To Here( 1 );

dtx = Current Data Table();

noRows = N Rows( dtx );

ddd = dtx << Get Rows Where( Column( dtx, 1 ) == "aaa" );

and the result is


[](0, 1)

note that this returns a 1


Column( dtx, 1 ) [1] == "aaa"

Does anyone have any idea what I am doing wrong?

thanks in advance

Heather

Re: get rows where returning empty matrix

Craige_Hales — Sat, 14 Mar 2015 03:17:44 GMT

I looks like Get Rows Where wants a simpler argument, try one of these


dtx=open("$sample_data/big class.jmp");

c=column(dtx,3);

dtx<<get rows where( dtx:c == "F" );


dtx=open("$sample_data/big class.jmp");

dtx<<get rows where( dtx:sex == "F" );

the odd looking returned value, [](0, 1), is JMP's empty array of 0 rows and 1 column. the two examples return more rows, of one column:

[1, 2, 3, 4, 5, 9, 10, 11, 16, 17, 18, 19, 20, 28, 29, 35, 36, 38]

Re: get rows where returning empty matrix

ms — Sat, 14 Mar 2015 08:13:19 GMT

A comparison of a Column object with a string will return always return false. In certain cases (or in general?) JMP must be expliticly told that you refer to a Column or to the Column values (I remember there has been a good thread about this maybe a little confusing difference but I can't find it now...)

You can access data with indices (as you showed above with Column( dtx, 1 ) [1] == "aaa"). In functions like Get Rows Where() that basically iterate through all column values, each value can be accessed with either of the below:

1) Column(dtx,1)[] == "aaa" // Note the empty brackets

2) As Column(dtx,1) == "aaa"

3) Or simplest with scoping colon as C Hales showed above

Re: get rows where returning empty matrix

h_lazar — Sat, 14 Mar 2015 10:50:10 GMT


dtx=open("$sample_data/big class.jmp"); 

c=column(dtx,3); 

dtx<<get rows where( dtx:c == "F" );

This did work, thank you both.

Re: get rows where returning empty matrix

Craige_Hales — Sat, 14 Mar 2015 12:25:38 GMT

cool. I didn't read the original question closely enough, and I'd forgotten about the empty [] anyway.