Trimming a matrix based on index values

So I have a large matrix where the first column is the time index, and all the other columns are data points at that time index. I want to be able to specific a beginning and end point for the time index (for example -70:50), and essentially get rid of everything outside of this range. I can use this code to get the values at a specific row, but im not sure of the most efficient way to include everything between the two starting points, but nothing else. Do anyone have an idea of the best way to do this?

a(a(:,1)==-70,[2:58])
a(a(:,1)==50,[2:58])

Thanks in advance

Answer 1

[Jan]

iniIndex = a(:, 1) == -70;
finIndex = a(:, 1) ==  50;
cut      = a(iniIndex:finIndex, 2:58);

Care about rounding errors, when the limit you are searching has no integer value. Then:

[dummy, iniIndex] = min(abs(a(:, 1) - 3.14159265));

[Victor Cabrera]

HI, I'm having an issue applying the last line of the first set of code. Matlab says that the ":" in

cut      = a(iniIndex:finIndex, 2:58)

is an invalid operator. I also don't understand the function of "2:58). Could you clarify. Thanks.