no output when coding

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

[Adam]

So what is your question?

[Stephen23]

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]

still no plot

aim is to work out the difference between each time interval then divide the subsequent difference from dt to produce a graph

[Adam Danz]

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]

(Answers Dev) Restored edit

Answer 1

[Hank]

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?

[Adam Danz]

+1, but with some changes.

1. dt needs to be dti
2. 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.
3. 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]

I'm a bit confused now, this is the eq i'm trying to solve.

I need it to be consecutive values so i dont think rand would be useful to me.

so which of these codes would work?

Also why is it to end-1 and not end?

[Stephen23]

"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]

apologies, thought i attached the data