explain ppamp=(max(wave(i,1:381))-min(wave(i,1:381))); in matlab

This line of code calculates the peak to peak amplitude (ppamp) of a signal wave at the i-th index.

The max and min functions are used to find the maximum and minimum values of the signal for the first 381 samples, respectively. Then the difference between the max and min values is calculated using the subtraction operator - and stored in the variable ppamp.

Note that the wave variable seems to be a matrix, where each row corresponds to a different signal trace, and i specifies the row index for which the peak to peak amplitude is being calculated.