This must be a FAQ, but I can't find it on the forum, in the docs, or the tutorials. Please direct me to the appropriate place -

I have a lot of data to import into the spreadsheet, and because of the way it is imported, I have a lot of arithmetic to do on rows, rather than columns. For example, in one data set I want to take a weighted average of the values in a row, with same weight for every element in the same column, and I want to repeat this on many rows. In another case I have to do more complex operations, adding, subtracting, multiplying different values in the same row, again repeated on each row.

All of the documentation and tutorials I have seen tell you how to do arithmetic on columns, but not rows. I did find a way to do this using a matrix, but that doesn't work well for me because the matrix is rather inflexible - once you create one, there isn't much you can do with it.

So is there a simple way to do this? For example to add the values in columns A, B, and C, subtract the value in D and store the answer in E?

Thanks.