How to replace a row in one matrix with a particular row from a different matrix

I have one large matrix (64800x40) with an index number, latitude, longitude, and other data for the remaining columns.

Ex.

[ Index      Lat      Lon      Data1       Data 2;
  25102      -45.5    51.5       3           4;
  25103      -45.5    52.0       4           7;
  25104      -45.5    52.5       10          4;
  25105      -45.5    53.0       12          2]

I've got another matrix with the same sort of data that I would like to use to replace particular rows in the first matrix. However, the second matrix is not the same size as the first (39x40).

Is there a script to run that would replace the data in the first matrix with the data from the second matrix? Perhaps using the index number?

[Rik]

You seem to be on the right track. You are nearly at a working solution (although you are closest to a very inefficient method). What have you tried?

Answer 1

[James Tursa]

Something like this maybe does what you want:

A = your large matrix
B = your smaller matrix
[y,x] = ismember(B(:,1),A(:,1));  % find where the indexes match in the 1st column
x = x(y);  % save only the row numbers where the indexes match
A(x,:) = B(y,:);  % replace the rows where the indexes match

[Chris H]

This worked well! Thank you so much!