I have a .dat file (which is actually a csv), whose columns are like

```
x1 y1 z1 w1
x2 y2 z2 w2
x3 y3 z3 w3
. . . .
. . . .
```

I want to separately obtain contour plots of `z(x,y)`

and `w(x,y)`

from the set of data.

I have imported the file with

```
mydata = Import("filename.dat","CSV");
```

Now I can form the vectors containing x, y, z values with

```
x = mydata((All, 1));
y = mydata((All, 2));
z = mydata((All, 3));
```

How to do the contour plot? The `ContourPlot`

function works with a function, not points.

I don’t necessarily need to interpolate between the points to make it a smooth function. If there is some way to plot densities at discrete points, that will also do. However, if there is a way to do this with interpolation, or if there is some inbuilt routine to achieve this, I am also interested to know about that.

The function `ListContourPlot`

requires a `n x 3`

matrix, but my data is `n x 4`

. How can I select a column specifically?