Specify a result file and resample the containing data by changing the interval and redefining the time frame. Increasing the output interval is useful to make result files smaller in size and to smoothen the corresponding graphs.
If you merge files from different load tests, the start times of those files are different, so use the Relative merge type.
If you click Absolute, you can specify a time frame. Only data within this time frame is merged into the target file.