How to import huge irregular xyz data set from excel and create gridded matlab matrix,

Dear all, Completely new to matlab and would love some assistance.

I have 3 columns of data in excel, x,y,z. This data is not gridded.

x ranges from 0-1500
y ranges from 0-1500
z ranges from 0-200

Total number of rows is 150,000

I have worked out how to import this data as vectors and can see i have 3 variables in matlab, x, y and z

These are displayed individually. For example x is [150,000, 0]. y is [150,000 , 0] z is [150,000, 0] .

My question is how to i create a matrix that is gridded and assigns the z values to each pair of xy.

I then intend to plot this matrix as a contour.

The xyz data represent the surface of a concrete sample that has surface damage

x = width, y=height, z = depth

I would appreciate a complete detailed example.

I thankyou in advance for your help

Kindest Regards

Maurice

Answer 1

[Image Analyst]

Try this:

numbers = xlsread(filename);
x = numbers(:,1);
y = numbers(:,2);
z = numbers(:,3);
% Find max values of the data so we can scale 
% to rows and columns indexes in the image we'll create.
maxx = max(x);
maxy = max(y);
% Find out how many rows (data observations) there are in the data.
numberOfRows = size(x,1);
% Define the size of the image you want to create.
columns = 800
rows = round(columns * maxy / maxy)
% Initialize an image to take the z values.
yourImage = zeros(rows, columns);
% Assign all the z values at the proper (x,y) location.
for row = 1 : numberOfRows
  thisRow = 1 + round((rows-1) * x(row) / maxx);
  thisColumn = 1 + round((columns-1) * y(row) / maxy);
  yourImage(thisRow, thisColumn) = z(row);
end
% Display the image.  Be sure to use imshow() with the [] option.
imshow(yourImage, []);