# How to concatenate 5x2 array output from my function?

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Mitchell Barclay on 22 May 2022
Commented: Rik on 23 May 2022
I'm using a function to perform some data manipulation across 5 datasets. The data is cyclic voltammetry, so basically rectangles with x and y values. My function is outputting the values I want into a 5x2 array which works fine for single input. I want to use a for loop to have multiple inputs and have the output of the for loop in a single tall Yx2 array. currently, my 5x2 output is simply being overwritten every iteration.
How can I make sure that each iteration is stored in the same array so that it grows over the course of the for loop?
function Currents = Dunn(data1, data2, data3, data4, data5, potential, tolerance)
%Find the values near specified potential value. This step is needed since my data does not have 0.6, 0.61, 0.62...
%so I needed to use a net around the chosen value.
A = data1(:,1)>(potential -abs(potential)*tolerance) & (potential + abs(potential)*tolerance) > data1(:,1);
B = data2(:,1)>(potential -abs(potential)*tolerance) & (potential + abs(potential)*tolerance) > data2(:,1);
C = data3(:,1)>(potential -abs(potential)*tolerance) & (potential + abs(potential)*tolerance) > data3(:,1);
D = data4(:,1)>(potential -abs(potential)*tolerance) & (potential + abs(potential)*tolerance) > data4(:,1);
E = data5(:,1)>(potential -abs(potential)*tolerance) & (potential + abs(potential)*tolerance) > data5(:,1);
%initiate placeholder vectors that will later be concatenated.
placeholderA = [];
placeholderB = [];
placeholderC = [];
placeholderD = [];
placeholderE = [];
%initiate counters for the for loops
a = 1;
b = 1;
c = 1;
d = 1;
e = 1;
%Identify max y-axis value at specified 'potential' (x-axis) value for each dataset.
for i = 1:length(data1)
if A(i,1) > 0
placeholderA(a,1) = data1(i,1);
placeholderA(a,2) = data1(i,2);
a = a+1;
end
end
for i = 1:length(data2)
if B(i,1) > 0
placeholderB(b,1) = data2(i,1);
placeholderB(b,2) = data2(i,2);
b = b+1;
end
end
for i = 1:length(data3)
if C(i,1) > 0
placeholderC(c,1) = data3(i,1);
placeholderC(c,2) = data3(i,2);
c = c+1;
end
end
for i = 1:length(data4)
if D(i,1) > 0
placeholderD(d,1) = data4(i,1);
placeholderD(d,2) = data4(i,2);
d = d+1;
end
end
for i = 1:length(data5)
if E(i,1) > 0
placeholderE(e,1) = data5(i,1);
placeholderE(e,2) = data5(i,2);
e = e+1;
end
end
%concatenate the max y-value for each placeholder array into the output of the function as a 5x2 array.
Currents = [max(placeholderA);max(placeholderB);max(placeholderC);max(placeholderD);max(placeholderE)];
In my .m file I call the function with:
i = 0.5;
for n = 1:100
Currents = Dunn(mvs10, mvs30, mvs60, mvs100, mvs200, i, 0.01)
i = i +0.005
end

Rik on 22 May 2022
This should already get you most of the way there:
i = 0.5;
for n = 1:100
Currents{n} = Dunn(mvs10, mvs30, mvs60, mvs100, mvs200, i, 0.01);
i = i +0.005;
end
##### 2 CommentsShowHide 1 older comment
Rik on 23 May 2022
Glad to be of help. If I solved the problem, please consider marking my answer as accepted answer. If you have any further questions, feel free to comment.