Look up corresponding element in a matrix

I have a matrix with multiple stations IDs and associated coordinate values along the stations rows (Matrix 1).

I have another matrix (Matrix 2) that in the first row has the "from" stations and in the second row has the "to" stations.

Using the station numbers specified in Matrix 2 (for both the from and to stations ), I need to look up the two station numbers from Matrix 1 and call the X-coordinates and Y-coordinates.

Is there a search function that will search for a number in a column and return the elements location of that matrix?

Answer 1

[Image Analyst]

Try this:

clc;    % Clear the command window.
clear all;
workspace;  % Make sure the workspace panel is showing.
format long g;
format compact;
matrix2 = randi(9, 2, 10);
matrix1 = randi(9, 20, 3);
numColumns = size(matrix2, 2);
xFrom = zeros(1, numColumns);
yFrom = zeros(1, numColumns);
xTo = zeros(1, numColumns);
yTo = zeros(1, numColumns);
for station = 1 : numColumns % for every column in matrix 2...
  fprintf('Examining column %d...\n', station);
  % Get the station number in this column
  fromStation = matrix2(1, station)
  toStation = matrix2(2, station)
  % Find rows in matrix 1 where the "fromStation" is located.
  fromRow = find(matrix1(:, 1) == fromStation);
  % Find rows in matrix 1 where the "toStation" is located.
  toRow = find(matrix1(:, 1) == toStation);
  % Now assume that the From station and To station are just one value each
  % Get the x and y coordinates from the "from" station.
  if ~isempty(fromRow)
    xFrom(station) = matrix1(fromRow(1), 2);
    yFrom(station) = matrix1(fromRow(1), 3);
  end
  % Get the x and y coordinates from the "to" station.
  if ~isempty(toRow)
    xTo(station) = matrix1(toRow(1), 2);
    yTo(station) = matrix1(toRow(1), 3);
  end
end

[Image Analyst]

Justin's "Answer" transferred here.

Thankyou Image Analyst,

I was able to get this part of my code to work based on your above example.

What is the reason I can not transpose the (1,n) xFrom, yFrom, xTo and yTo matrices to be (n,1) vectors?

[Image Analyst]

You should be able to transpose column vectors into row vectors and row vectors into column vectors with the ' operator:

xFrom = xFrom';

and so on. Since you said it's working, can you go ahead and mark the answer as Accepted? Thanks.