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Sum of a column where column name is stored in a variable

akrishna39

Hi,

I have a variable named as "target var" which stores the column name "diameter". When I do show(target_var), I get the output "target_var = :diameter". Now, I want to find the sum of the column whose name is stored in the variable "target_var". But when I do sum(eval(target_var)), I get "Column Disappeared{1}" in the log. Only when I do sum(diameter), I get the correct result. How can I sum the column using the variable target_var? Please help.Thanks!!

Accepted answers

Try saving the name of the first column as a string using << Get Name, and then specify the table and column name in the Col sum function. Here is an example:

//Open one table
dt1 = Open( "$Sample_data/Big Class.jmp" );

//Get the name of a column as a string
target_var = Column( dt1, "height" ) << Get Name;

//Open another table
dt2 = Open( "$Sample_data/Big Class Families.jmp" );

//Get a reference to the column in the second data table
field_data = Column( dt2, "height" );

//Sum the column using a reference to the column in a specific data table
ysum = Col sum( field_data );

Edited to use field_data in Col sum function.

All comments

txnelson

If I understand your current situation, your value of the variable Target_var is:

"target_var = :diameter"

To execute that literal string, you will need to run

Eval(Parse(Target_var));

The result of this will make the value of Target_var

:diamiter

You should then be able to run your code

sum(eval(target_var))

pmroz

Did you want to use colsum instead of sum? This works:

target_var = "Diameter";
colsum(column(target_var));

Note that target_var is pointing to the string "Diameter", not the column :Diameter.

akrishna39

Hi Jim,

Actually target_var is not stored as a string. I have defined target_var as follows:

target_var = column(6);

The name of my 6th column is "diameter". So I think taget_var is storing the name of the column as an expression rather than a string. When I execute the following code, i do not get double quotes on diameter:

show(target_var);

The output of the above code is just target_var = :diameter. There are no qutations. So, let me know if I can sum the column corresponding to target_var now. Thanks

akrishna39

Hi pmroz,

Actually this also has the same problem that I told Jim about. Please let me know if I can take the column sum if my target_var stores the column name as an expression and not as a string. Thanks

txnelson

Here is a short script that uses what I believe uses your

target_var = column(6);

The script uses it in a calculation and in a Platform

names default to here(1);
dt=open("$SAMPLE_DATA/semiconductor capability.jmp");

target_var = column(6);

thesum=col sum(target_var);
show(thesum);

Distribution( Continuous Distribution( Column( target_var ) ) );

How are you attempting to use this in a Sum() function as you have indicated. Can you please provide some sample code of your efforts?

akrishna39

Hi Jim,

Thanks, your script works fine. But I think I am having trouble due to another reason. I am defining target_var in a data table. Then I am trying to sum the column defined in target_var in another data table which also has the column name stored in target_var. Below is my code:

//Opening a data table
comp_data=open(path || comp_data_filename);
nc = ncols(comp_data);
target_var = column(nc);  //Defining target_var
close(comp_data);
//Closing the data table

//Opening another data table
field_data=open(path || field_data_filename);
ysum = colsum(target_var); //This line does not work. I get an error saying "Column disappeared". 
//JMP is not able to find the same column name in this new data table

Please let me know if this can be solved. Thanks!!