Need help with Mata function

[Ibrahim Filiz]

Hello,

I need help with this Mata task: Write a Mata function returning the sum of all odd elements of a vector (e.g. if the vector is x={1,2,4,7,5,6}, the function should return the solution of 1+4+5). The function should work for both column and row vectors (i.e. you need to use an if condition in your code). It is not necessary to embed this function in a Stata program. A simple Mata function for the use in Mata is sufficient.

Is the following function correct:

clear mata
mata

function task3(real vector x) {

real scalar i
real scalar n
real scalar r
real scalar c

r = rows(x)
c = cols(x)

if (c == 1) {
n = r
X=J(1,1,.)
}
if (r == 1) {
n = c
Y=J(1,1,.)
}
for(i=1; i<=n; i = i + 2) {
X = sum(i+i)
Y = sum(i+i)
}

return(X)
return(Y)
}

x = (1,2,4,7,5,6)
task3(x)

end


Thanks,
Ibrahim

[Niels Henrik Bruun]

You might get inspiration from:

: mata clear

: function get_sum_odds(real rowvector x) return(mod(1..length(x), 2) * x')

: x= 1,2,4,7,5,6

: get_sum_odds(x)
  10

I leave it to you to make the code handle both row and col vectors

[Ibrahim Filiz]

Dear Niels, Do you think my code is wrong?

[Niels Henrik Bruun]

Not necessarily, I just thought you should use matrix notation to get what you wanted with less code

[Ibrahim Filiz]

Thank you.