Contour plot for given x,y,z

Dear All,

I have x, y, and z data. I was unable to plot 2D contour. 1st column is x, 2nd column is y and 3rd column is z. Kindly help.

[madhan ravi]

on which plane?

[Manish Kumar]

On xy plane

[madhan ravi]

why not contour() ?

[Manish Kumar]

i have tried

contour (x,y,z)

Error is:

Error using contour (line 48)

Z must be at least a 2x2 matrix.

Error in Untitled (line 1)

contour (x,y,z)

Answer 1

[KSSV]

[num,txt,raw] = xlsread('Book1.xlsx') ; 
x = num(:,1) ; 
y = num(:,2) ; 
z = num(:,3) ; 
figure(1)
scatter(x,y,20,z,'filled') ; colorbar
%% Method 1 / Griddata
nx = 500 ; ny = 500 ;
[X,Y] = meshgrid(linspace(min(x),max(x),nx),linspace(min(y),max(y),ny)) ;
Z =griddata(x,y,z,X,Y) ;
figure(2)
contour(X,Y,Z) ;
figure(3)
pcolor(X,Y,Z)
shading interp 
%% Method 2 simple reshaping 
x = unique(x) ; nx = length(x) ;
y = unique(y) ; ny = length(y) ;
Z = reshape(z,ny,nx) ;
figure(4)
contour(x,y,Z)