Thanks for the quick reply.
Here's a better description of my problem. I am importing data from a computational code and then plotting the results in Excel. The code I am using requires that I import ALL of the computed data into Excel, which can be thousands or even hundreds of thousands of rows. The difference in the data between each row is small, since, in one time-step, not much happens in the code. Thus, for accurate plotting, I do not need all of the data, just, say, one in every 5, 10, 100, etc. rows, depending on the size of the file (Excel can only plot 32,000 points on a 2-D plot). Thus, I would like to permanantly delete these points (rows), both to reduce the overall size of the Excel file, and to allow for plotting in Excel. I
I should not have used the term "filter". In escence, I would like to "sample" the data. "Undersampling" the data occurs when you are sampling a data set too slowly to accurately capture and recreate that set. In my case, I have entirely too much data to handle in Excel, and as long as I am careful (i.e., as long as I don't remove too much data), I will not undersample, and the plots I create in Excel will accurately reflect the computed data.
If need be, I can write a computer code to reduce my file size as I specify, but I thought that there may be an easy way to do this in Excel.
Thanks,
Haf