Hi,
In your mat file, F1 and V1 are cells, not arrays. A cell is an object that can contain numbers, strings, ... there is no sense to "add" cells.
you need to extract the data you want from your cell, or convert it directly.
something like that :
load FDR_0.2.mat;
dp=6000:8000;
c=x(dp);
d=cell2mat(F1(dp)); % convert in array
A=polyarea(c,d);
figure, plot(c,d)
