Got it
filename = 'Graph.xlsx';
sheet1 = 'Sheet1'; %All ISINs in the portfolio
xlRange1 = 'A2:C108';
scoreData = readtable(filename,'Sheet','Sheet1','Range','A2:C108','ReadVariableNames',true);
scoreData2cell = table2cell(scoreData);
M=cell2mat(scoreData2cell(:,2:3));
[~,Header]=ismember(scoreData2cell(:,1),unique(scoreData2cell(:,1)));
K=accumarray([M(:,1),Header],M(:,2));