I'm sorry, but waiting for us to tell you what the format is for your input data seems extremely backwards. You should be able to either show us the format that is used to print the last field in your input file, show us the output for a data sample with a negative imaginary part, or explicitly state that there will NEVER be any negative imaginary parts.

In addition to what RudiC suggested and assuming that if there are any negative imaginary parts in your complex numbers, they use a - instead of a + to separate the real and imaginary parts; you could modify your sed command to cover both cases (assuming you are using a standards conforming sed with an extension that allows multiple substitute commands to be separated on one line by a semicolon [as was used in your code]):

Code:

sed 's/\([0-9]\)\([-+][0-9]\)/\1, \2/; s/i//' eps.out > eps2.out

or, if there could be more than one complex number on a line:

Code:

sed 's/\([0-9]\)\([-+][0-9]\)/\1, \2/g; s/i//g' eps.out > eps2.out

If you're using a GNU sed which does not always adhere to the standards, you might need to use:

Code:

sed --posix 's/\([0-9]\)\([-+][0-9]\)/\1, \2/g; s/i//g' eps.out > eps2.out

to make it work. If you would tell us what operating system and shell you're using when you submit questions like this, those of us trying to help you would be able to determine which code suggestion might work for you without making assumptions about what OS you might be using.