no output when coding
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a = xlsread('outdoorall.xlsx','H2:H52364');
b=xlsread('indoorall.xlsx','H2:H52364'); %2397
t=xlsread('outdoorall.xlsx','E2:E52364');% time in secs
for i=1:2363
dti=t(i+1)-t(i);
dt=(b(i+1)-b(i))/dti; % change in indoor temperature divided by time
c=dt/a(i)-b(i);
plot(c)
end
the idea is each time step is different so i want to divide the change in temp by each unique time step
5 个评论
Adam
2020-2-10
So what is your question?
Stephen23
2020-2-10
As c is scalar the plot will look empty (it isn't actually, as it contains one line with one point and no marker). All loop iterations are entirely replaced by the next iteration, so only the last one will remain plotted in the axes (all one invisible point of it!).
Probably you should plot after the loop, then you will actually see something.
Boss Man
2020-2-11
Copy of question
a = xlsread('outdoorall.xlsx','H2:H52364');
b=xlsread('indoorall.xlsx','H2:H52364'); %2397
t=xlsread('outdoorall.xlsx','E2:E52364');% time in secs
for i=1:2363
dti=t(i+1)-t(i);
dt=(b(i+1)-b(i))/dti; % change in indoor temperature divided by time
c=dt/a(i)-b(i);
plot(c)
end
the idea is each time step is different so i want to divide the change in temp by each unique time step
___________________________________________________________
My comment
Try
c = nan(1, 2363);
for i=1:2363
dti=t(i+1)-t(i);
dt=(b(i+1)-b(i))/dti; % change in indoor temperature divided by time
c(i)=dt/a(i)-b(i);
end
plot(c)
or
hold on
for i=1:2363
dti=t(i+1)-t(i);
dt=(b(i+1)-b(i))/dti; % change in indoor temperature divided by time
c=dt/a(i)-b(i);
plot(c, 'o')
end
Rena Berman
2020-5-14
(Answers Dev) Restored edit
采纳的回答
Do this without a for loop
% Load data
a = xlsread('outdoorall.xlsx','H2:H52364');
b=xlsread('indoorall.xlsx','H2:H52364'); %2397
t=xlsread('outdoorall.xlsx','E2:E52364');% time in secs
a = a(:); b = b(:); t = t(:); % make sure we're working with column vectors
dti = diff(t) % difference between each value of t, length is one less than 1;
% it looks like your formula is the difference in db/dt divided by the difference between a and b.
% Pad db/dt with 0 so the array length matches with a and b.
c = [0; diff(b)./dt] ./ (a-b) ;
plot(t,c)
is this what you're trying to do?
4 个评论
+1, but with some changes.
- dt needs to be dti
- Instead of padding the 0 in c, remove the last values in a and b to match what the loop is doing. Note, it may be the case that the padding is actually what the OP intended to do and it would preserve the number of data points.
- In the loop, c=dt/a(i)-b(i); dt is divided by a, not divided by (a-b). Again, the OP should carefully decide which is needed.
a = a(:); b = b(:); t = t(:);
dti = diff(t)
c = (diff(b)./dti) ./ a(1:end-1) - b(1:end-1) ;
plot(c)
% or
% plot(t(1:end-1),c)
Compare results
% OP's loop (cleaned up)
t = rand(400,1);
a = rand(400,1);
b = rand(400,1);
c = nan(1, numel(t));
for i=1:numel(t)-1
dti=t(i+1)-t(i);
dt=(b(i+1)-b(i))/dti; % change in indoor temperature divided by time
c(i)=dt/a(i)-b(i);
end
clf()
subplot(2,1,1)
plot(c)
title('OP''s Loop')
% Vectorized version
dti = diff(t)
c = (diff(b)./dti) ./ a(1:end-1) - b(1:end-1) ;
subplot(2,1,2)
plot(c)
title('Vectorization')
Boss Man
2020-2-11
Stephen23
2020-2-11
"I need it to be consecutive values so i dont think rand would be useful to me."
You did not provide a, b, or t, so Adam Danz quite reasonably just used some matrices of random values in order to actually run the code on something.
You should use your own arrays, of course, not the random values that are just used for testing.
Boss Man
2020-2-11
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