MATLAB: Matrix look up issue

matrixmatrix lookup

I have a large matrix which has RPM in the first column and Torques populating the rest of the matrix. I need help finding a way to search the first column for a set rpm and then search that row for value of torque, from that i need the position of that value in the matrix to then find an efficiency value in an identical sized matrix.
I have so far:
RPM_val =1000; [row] = find(T_T==RPM_val)
This gives me the row where the 1000rpm is, how do i then search just that row for the value of torque i am after,or the nearest value to it.
Thank you

Best Answer

Time to learn about matrix indexing?
[row] = find(T_T==RPM_val)
First of all, this searches the ENTIRE matrix for a value equal to RPM_val. If it turns out that another column happens to hit that value, you will get the wrong answer. While that might be a spectacularly unlikely event, or so you think, something as silly as this is the source of many a bug. Good code avoids obvious bugs by careful planning.
So instead, do this:
[row] = find(T_T(:,1)==RPM_val);
That searches only the first column. Be careful though. What is there is no exact match? find will return empty then. Do you want to find the closest?
Once you do have the row, then consider what this does:
T_T(row,2:end)
That extracts a vector of elements only in the indicated row, excluding the first column. How might you use that in a secondary search using find?
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