The contour function requires Z=f(x,y); I have measured data for X,Y, and Z that are not related with a function. I get errors when I use Z as a X:1 array

contour

I am tryong to get a contour map with excel data: The error message reuires Z to be at least a 2x2 matrix not a x:1. How do I convert the Z data to be used with the contour functions?

RA(X) DEC(Y) Peak S/N (Z)

0 -40 1.01

1 -40 1.05

2 -40 0.82

3 -40 0.94

4 -40 0.97

5 -40 0.85

6 -40 0.89

7 -40 0.94

8 -40 1.21

9 -40 2.37

10 -40 2.74

11 -40 1.65

12 -40 1.46

[Walter Roberson]

Your Y values are all the same. You cannot contour that posted data.

Answer 1

[Bjorn Gustavsson]

You will have to look at the scatteredInterpolant or TriScatteredInterp and possibly also its related griddata functions, check the help and documentation for those functions - they will let you re-interpolate your scattered data onto/into regularly spaced points in RA and DEC. You might also find these functions on the file exchange useful:tricontf, contour-plot-for-scattered-data and contours-for-triangular-grids.

If you have data on a regular grid you can always use the reshape functions to put your 3 variable into an [n_RA x n_DECL] grid and use the contour-function.

HTH