sarl = readobj(something)
Pass the content of the variable called something to the function readobj. If readobj expects a filename, the content of that something better be a file name. Of course, if you don't have a variable called something, then matlab will error with undefined variable "something".
sarl = readobj('something') %Note the ''
%or
sarl = readobj("something") %in R2016b or later
Pass the text something to readobj.
Two completely different things.
You meant:
sarl = readobj('butan.obj');
%or
sarl = readobj("butan.obj");
