How can I get a coloured contour plot from a excel data sheet?

I have an excel data sheet of x,y,z . The value of z depends on x ,y however there is no such equation which relates z with x and y.

[KSSV]

What you have done so far? Have you read the excel file using xlsread? Read the data using xlsread. You will get the data. Arrange them into a matrix. Use contour(X,Y,Z) .

[SWAGATA BHUNIA]

I have read the xlsread. When I am trying to get a contour by using the command contour(x,y,z), there some error is coming. As it is not a surface,there are lots of curve,which gives a surface like structure in 3d.

[Walter Roberson]

What error message are you seeing?

Do your x and y form a rectangular grid, or are they scattered around?

[SWAGATA BHUNIA]

By using contour(x,y,z) I am getting the error "z must be a 2*2 matrix". Yes, the x and y form a rectangular grid but they are not equal spacing.

[Walter Roberson]

Your xlsread() would probably return a something-by-3 array of values, with the columns being x, y, and z coordinates. You need to reshape() all three of those the same way, to form a rectangular grid; it is not required that the x or y be equal spacing, only that the values be sorted and consistent.

For example,

x = sort(rand(1,20));
y = sort(rand(1,15));
[X,Y] = ndgrid(x,y);
Z = sin(pi*X) + cos(pi*Y);
contour(X,Y,Z)

The x and y values are not equally spaced, but the grid that is formed is rectangular, and that is good enough for contour.

[SWAGATA BHUNIA]

Firstly, there is no such function which relates z with the x and the y I have plotted this file by using origin pro, from where I saw the rectangular grid. In matlab I don't know how to form a rectangular grid. Can you tell me this? Should I convert this x,y,z to a matrix (xyz gridding) if so then what is the algorithm?

[Image Analyst]

That was just an example. Your z can be anything. The point is you need an N by 3 array of x, y, and z values, or you need 3 separate N by 1 vectors for x, y, and z. What does it say if you do this

size(x)
size(y)
size(z)

[SWAGATA BHUNIA]

I have stored data of x in a column matrix(n*1) and similarly for y data. Z value has been stored in a two dimension array. Now the problem is the command contour(x,y,z) is not working because of my repeated x data. Is there any solution for this?

[SWAGATA BHUNIA]

Thanks, I have done this by using meshgrid and it is coming nice.

[Amalkrishnan K]

will u tell me how u did it using meshgrid?...am having the same prob of matrix