create a variable from 1x1 matrix elements

[Stan Peterburgsky]

Hello,

I would like to create a variable from 1x1 matrix elements. Specifically, I have matrices A1, A2, ... A100, each of which is a 1x1 matrix. I would like to create a variable B where the first observation is A1's value, the second observation is A2's value, and so on, with 100th observation being A100's value. I just don't know the syntax (I don't have much experience with Stata's matrices). Please help.

Thank you,
Stan

[Clyde Schechter]

gen B = .
forvalues i = 1/100 {
    replace B = A`i'[1,1] in `i'
}

This assumes that your data set already contains at least 100 observations. If it does not, you have to first -set obs 100-.

[Stan Peterburgsky]

Thank you, I didn't realize this requires a loop.

I noticed that if my matrices are instead named A1001, A1002, ..., A1100, the following code does not work (error: 'j' invalid observation number):

 gen B = .
forvalues i = 1001(1)1100 {  
     scalar j = `i' - 1000 
     replace B = A`i'[1,1] in j
}

I don't understand what's wrong with the code. Any ideas? Thank you.

[Nick Cox]

You would be better off using a local macro and then you need the surrounding quotation marks, just as in Clyde Schechter 's example in #2. Stata won't evaluate a scalar on the fly in that context without a strong push.

gen B = .  
quietly forvalues i = 1001(1)1100 {        
    local j = `i' - 1000        
    replace B = A`i'[1,1] in `j'  
}

[Stan Peterburgsky]

Thank you very much for your help!