For loop output as an array

Question

I wrote a code in Matlab which I predefine the variable "a" and then set up a for loop of 5 iterations where the variable "a" goes through some basic operations. However, the for loop output only saves the fifth iteration of "a." How do I save all 5 iterations in a 1x5 array?

The code is as follows:

a = 10;
k = 0.5;
n = 2;
for m = 1:5
    a = a + (a*k) + n;
end

Edit: I just found it that I have to create a new variable.

a = 10;
k = 0.5;
n = 2;
a_n = zeros(1,5);

for m = 1:5
    a = a + (a*k) + n;
    a_n(m) = a;
end

.. What language is that? Without knowing, I don't know what the syntax is to create an array. (Of course you could use Google with "[language] array".) — Jongware
– Jongware, Commented Oct 17, 2013 at 18:27
Declaration of new variable a_n = zeros(1,5); is redundant in Matlab — jkshah
– jkshah, Commented Oct 17, 2013 at 18:52

jkshah · Accepted Answer · 2013-10-17 18:37:37Z

2

You may need to store value of a after each iteration into an another variable x

a = 10;
k = 0.5;
n = 2;
for m = 1:5
    a = a + (a*k) + n;
    x(m) = a;
end
x

Output:

x =
    17.000    27.500    43.250    66.875   102.312

answered Oct 17, 2013 at 18:37

jkshah

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1 Comment

Praveenram Balachandar Over a year ago

The array syntax is correct on this answer. This should be the chosen answer.

Praveenram Balachandar · Accepted Answer · 2013-10-17 18:46:38Z

1

You would need to use a different variable to store the 5 iterations as an array.

Code would look something like this:

a = 10;
k = 0.5;
n = 2;
b = [];
for m = 1:5
   a = (a + (a*k) + n)
   b = [b a];
end

You can now print b for all 5 iteration values.

Here is an alternate way to update values into the 1-D matrix.

edited Oct 17, 2013 at 18:46

answered Oct 17, 2013 at 18:28

Praveenram Balachandar

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5 Comments

Ash Burlaczenko Over a year ago

How do you know what language this is?

Praveenram Balachandar Over a year ago

Based on the syntax of for loop I guessed Matlab, but I could be wrong here.

Praveenram Balachandar Over a year ago

Terry, please choose the other answer as the chosen answer, it has the proper array syntax. I'll update my answer with that change as well.

jkshah Over a year ago

@PraveenramBalachandar apart from the syntax, your code won't give desired output. it's not storing previously processed value of a for next iteration

Praveenram Balachandar Over a year ago

You're right, I overlooked that as well. Thanks, I'll fix it.

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