Problem 1911. Find the index of the first occurrence of a value in a matrix

Given a matrix of scalars, find the first occurrence of -1 in each column. Output NaN for a column which does not contain the value. For example

 input =

     0     0     0     0
    -1    -1     0     1
    -1     1     0    -1
     0     0     0     1

Find row number of first instance of -1 in each column

 output = [2 2 NaN 3]