Request for Guidance on Gnuplot Procedure

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Request for Guidance on Gnuplot Procedure

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As a new gnuplot user I am asking veteran gnuplot users to consider my need and point me in the right direction. Gnuplot plot is obviously a very versatile tool and does many things. Please help me avoid reading the mass of documentation just to find the small portion that best meets my need. I suspect my requirements may be very familiar to experienced gnuplot users.

I want to create what I'm told is called an "intensity plot" in some programs, such as Matlab. By "intensity plot" I mean a black-and-white flat image area (grayscale?) that is dark in some regions and light in others. I want to create the image from a text file that has three columns of data. The first two columns represent X and Y positions. The third column is the Z (intensity) value. All data are decimal values (ie not integers).

From what I've read so far 3D gnuplot data file format requires a blank line after each group of data that forms a column on the intensity image. It will be difficult for me to insert the blank lines so I don't want to do it unnecessarily. What is the blank line for anyway? Is it like a newline character in a text file?

I would also like to know if gnuplot processes data files line-by-line, or does it read and store the entire file prior to processing? My data file is about 1.2GB in size. I feel this size may be a problem if gnuplot has to store all the data in memory at once.

References to appropriate examples, documentation, or commands would be ideal.

All help/comments/recommendations are greatly appreciated.