how to get multiple values of multiple columns from a single column?

I have a 100x100 matrix where the first column is time and the remaining 99 are % (from 0 to 100%). I would like to know the time value (column 1) where each column reaches the value 40 (40%).

Thank you very much.

Answer 1

[Dyuman Joshi]

Use logical indexing - Find Array Elements That Meet a Condition, for columns 2-100

(Assuming the value 40 occurs same number of times in each column)

You can also use min -

%sample data
y = magic(5)

y = 5×5

17 24 1 8 15 23 5 7 14 16 4 6 13 20 22 10 12 19 21 3 11 18 25 2 9

%closest value to 16
[v, k] = min(abs(y-16))

v = 1×5

1 2 3 2 0

k = 1×5

1 5 3 2 2

For columns 1:size(y,2) and the corresponding values in k, i.e. row values, are the closest to 16

s = size(y);
y(sub2ind(s, k, 1:s(2)))

ans = 1×5

17 18 13 14 16

[Dyuman Joshi]

Any updates, @Juan Antonio?