MATLAB: Distances along a plotted line

Question

I have x and y matrices with y representing elevations at points x.

For instance

   x = [0 5 10]
   y = [2 4 1]

plot(x,y) gives me a cross section of elevations.

I want to mark various distances along the plotted line. For instance, place a marker every 1m along the line, or put individual markers at specific distances along the line.

How can I do this?

Thanks!

Answer 1

   marker_dist = 1;
   x = [0 5 10];
   y = [2 4 1];
   dist_from_start = cumsum( [0, sqrt((x(2:end)-x(1:end-1)).^2 + (y(2:end)-y(1:end-1)).^2)] );
   marker_locs = marker_dist : marker_dist : dist_from_start(end);   %replace with specific distances if desired
   marker_indices = interp1( dist_from_start, 1 : length(dist_from_start), marker_locs);
   marker_base_pos = floor(marker_indices);
   weight_second = marker_indices - marker_base_pos;
   marker_x = x(marker_base_pos) .* (1-weight_second) + x(marker_base_pos+1) .* weight_second;
   marker_y = y(marker_base_pos) .* (1-weight_second) + y(marker_base_pos+1) .* weight_second;
   plot(x, y);
   hold on;
   plot(marker_x, marker_y, 'r+');
   hold off