How to plot a contour

i have a problem regarding contour plot,for inbuilt contour function contour(A),A has to be a matrix, but in my problem geometry is irregular and i am using Element free Galerkin method. So at each step i am having different number of nodes and can't form a matrix to input.Please tell me how can i plot contours without having a input matrix.

[Fangjun Jiang]

Show some example data please.