For this error message, it seems that you have a variable named 'xlim' conflicting with the built-in MATLAB function 'xlim'.

If this is the case, rename your variable 'xlim' to any other name, run your program again and post your results (success or not) here.

This type of plot shouldn't be too hard to create without external toolkits. Concerning the methods to plot your data:

I am assuming that by irregular network you mean the data is not equally distance distributed, is that correct? I believe also that you are willing to interpolate your missing points with the existing data.

You want to plot graphical images of SST and SSS, which are 2D horizontal maps depicting the properties of the surface of the sea for a defined region, but CTD data usually contains values for multiple depth layers. Then, for each CTD profile you will have to get only the surface-most value of temperature or salinity.

After reducing each CTD profile as a triplet of X (e.g longitude), Y (e.g. latitude) and T (e.g temperature - for a SST map), you may organize all your X, Y and T values into 3 arrays: X_all, Y_all and T_all, where each line of these arrays will represent the information of one reduced CTD profile.

At this point you can interpolate your data to any 2D coordinate points using 'interp2':

>>T_new = interp2(X_all,Y_all,T_all,Xq,Yq);

where Xq and Yq are the grid coordinate points for your interpolated map for X-direction and Y-direction.

To plot you SST map you may use 'contour', 'contourf' or 'pcolor':

>>contourf(Xq,Yq,T_new);

This should generate your interpolated SST map.

Take care that you hardly can Obtain SST (sea SURFACE temperature) from CTD as you should usually discard first few meters in CTD data. At most you could interpolate maps of sea temperature at, let's say, 5 m depth, definitly NOT surface. :)

Concerning the error, as Ricardo said, you have a variable in workspace named as a matlab function, xlim. CHange the name of your variable.

Cheers

Antonio

Since you are working with a CTD, you can use depth information to figure out how close you are to the surface.  If your first measurements occur, for example, somewhere within the thermocline, then it may be difficult to extract information about the upper mixed layer.  Consequently, you will need to be careful about extrapolating to the surface.  Also, are there other surface observations you can compare with?  For instance, go on the National Data Buoy Center and find some buoys with SSTs near your location.  If you are close by you can do a quick comparison with any extrapolation methods you use.  If you are quite far away from a buoy, then I would advise to interpolate between two buoys that may act as two points sandwiching your location.  You will need to be careful here too since SST gradients can fluctuate depending on wind-wave interactions, upwelling, currents, etc.  You can also use satellite SST data provided by platforms such as MODIS to get an estimate on how well your method works.  

Just to note, many stations don't have SSS available.  You can use NASA's Aquarius to make somewhat of a comparison. 

Good Luck,

E. S.