Don't know how to fix

outdoorapr = xlsread('outdoorapr.xlsx','D2:D8586');
indoorapr=xlsread('indoorapr.xlsx','D2:D8586');
time=xlsread('time.xlsx','C2:C8586')
a=(outdoorapr);
b=(indoorapr);
t=time;
dt=diff(a)/5;
c=dt./(b(1:end-1)-a(1:end-1));%diff(a) will be one less than matrix a and b
plot(t,c);

when computing the time, i receive an empty matrix, attached are the files used, range for each of them is mentioned above. the graph produced doesnt have the time on the x axis and produces a strange curve. dont know where ive gone wrong

[Walter Roberson]

column C in time.xlsx is a macro; the actual times are stored in column B . That might make a difference in the reading.

I recommend that you switch to readtable() instead of xlsread() .

Which MATLAB release are you using?

[Boss Man]

Most recent 19b