# How can I write a for loop to do algebra over multiple arrays?

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Havi Tripathi on 20 Aug 2021
Commented: Havi Tripathi on 20 Aug 2021
I have 4 1x28 arrays.
I want to solve an equation for time, also linearly spaced as 1x28, for each value in this row.
a = linspace(3,28,28);
b = linspace(4,28,28);
c = linspace(5,28,28);
d = linspace(6,28,28);
time = linspace(1,28,28);
for i = 1:28:
value = a.*time ./ (c+d)
end
So, in the end, value should be a 28x28 array right. The first column of value, for example, should be value evaluated at time 1.
As it goes downward in column 1, it should be evaluated at time 2, etc till 28.
I'm not sure how to actually implement this. When I am doing it regularly, I get back a 1x28 array from value.
Does anyone know the approach or solution I am looking for?

Wan Ji on 20 Aug 2021
Do loop with indices of t:
a = linspace(3,28,28)';
b = linspace(4,28,28)';
c = linspace(5,28,28)';
d = linspace(6,28,28)';
time = linspace(1,28,28);
value = zeros(28,28);
for i = 1:28
value(:,i) = a.*time(i)./ (c+d);
end
And then the value becomes 28*28 as you want.
Havi Tripathi on 20 Aug 2021
Thanks for the quick help! I understand indexing better now.

Simon Chan on 20 Aug 2021
Try this:
A = arrayfun(@(x) x.*time./(c+d), a, 'UniformOutput', false)
result = cell2mat(A')

R2020b

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