The main motivation to use convones is to have a faster routine for the special case where one of the arguments of a one-dimensional convolution is a series of all-1 values.
convones - convoles a function with a number of consecutive ones
FORMAT: cfunc = convones(f, cnum [, w])
Input fields:
f function to convolve
cnum number of consecutive ones to use
w if 1x1 true, weight (divide by number of samples)
Output fields:
cfunc ones-convolved function
See also conv
The main internal use for this function is the creation of design matrices. Opposed to SPM (which typically uses a 16 timebin-per-TR resolution), the design matrix creation in NeuroElf uses a millisecond resolution. While differences between convolved time courses are small (the HRF does not have frequency components for which the maximally occurring shift would matter much w.r.t. their phase), I like the idea of being precise wherever possible. And since onset times are commonly given in milliseconds (and people seem to make a whole lot of fuss about stimulus timing these days), I figured it would be nice to have this implemented…
% create a large gaussian kernel k = smoothkern(2000); % convolve with a all-ones vector of equal length tic, ko = convones(k, numel(k)); toc % reference: Elapsed time is 0.024565 seconds. % and now the same with conv tic, koc = conv(k, ones(numel(k), 1)); toc % reference: Elapsed time is 0.240042 seconds.
Note: the difference gets larger the longer the vectors become!!