This won't work for a couple of reasons:
sprintf('C:\my\directory\...\Count_missing_values%d.fig',S(k).name)
- backslash (\) is an escape character for sprintf, i.e., an indicator of a special character such as \n (newline), \r (carriage return), \t (horizontal tab), etc., so you shouldn't use \ in your sprintf call unless you mean to indicate special characters such as the ones mentioned. You could replace all \ with \\ to escape the backslash and print a literal backslash, but an easier way would be to use %s to represent the first part of your file's full-path name (this is shown below).
- %d is not an appropriate format for S(k).name. Use %s to print a character array such as a file name.
Therefore, do something like this instead:
filename_prefix = 'C:\my\directory\...\Count_missing_values';
% ...
saveas(h1,sprintf('%s%s.fig',filename_prefix,S(k).name));
Note that that makes the file names all start with "Count_missing_values", which looks like what you're going for. If instead "Count_missing_values" should be the directory that contains the files, put another backslash on the end:
filename_prefix = 'C:\my\directory\...\Count_missing_values\'; % <- ends with \
% ...
saveas(h1,sprintf('%s%s.fig',filename_prefix,S(k).name));
