Probably the easiest:
geneswithdata = readtable('data.txt'); %load file as a table
geneswithdata.Properties.VariableNames{1} = 'genes'; %rename first column for clarity (optional).
%I would also rename all the other columns
genesonly = readtable('genelist.txt'); %load as a table
genesonly.Properties.VariableNames = {'genes'}; %rename columns. Common columns must have the same name
filteredgenes = innerjoin(genesonly, geneswithdata);
Done.
Using ismember that last line could be done as:
found = ismember(geneswithdata, genesonly);
filteredgenes = geneswithdata(found, :);
Using intersect (rather than setdiff) it could be done as:
[~, tokeep] = intersect(geneswithdata, genesonly);
filteredgenes = geneswithdata(tokeep, :);
