TV provides five commands to perform arithmetic operation on spectra, as there are:
tv s add idx {fname['fmt] {idx...} acti all show visi}
tv s subt idx {fname['fmt] {idx...} acti all show visi}
tv s mult fact {{idx...} acti all show visi}
tv s maxi idx {{idx...}} acti all show visi}
tv s mini idx {{idx...}} acti all show visi}
add summarizes the contents of all spectra specified by the second argument to the buffer defined by the first argument idx. As second argument it accepts an integer value by default which is interpreted as buffer number, or alternatively a text value which is taken as filename of a spectrum. The argument all makes TV to add all spectra but the one in the destination buffer. If the destination buffer was empty before, the spectrum will get the name of the first spectrum added.
subtract works analogous to add, but subtracts spectra.
multiply multiplies the spectra given by the last argument with the factor fact. The second argument takes an integer argument as default value.
maximum takes the maximum for each channel of all spectra defined by the last argument and puts this value in the spectrum specified by the second argument. The last argument takes integer values as default, which give the buffer-numbers for comparison.
minimum works analogous to maximum, but takes the minimum of each channel.