save values in array in a loop

I want to save a value calculated inside a loop in an array. Is it possible? for example:

for i=1:10
    s=a+b;
    a(i)=s;
 end
a

ans=
a=[23 45 678 21 34 134 34 56 11 34]

how to save s in an array so that this loop give an array containing the calculated values?

[Stephen23]

It is not clear what you are trying to do. Which variables do you already know the values of? What are the values of a and b ? Is the operation just a simple addition?

You should consider vectorizing the calculation rather than doing this in a loop. This would likely be neater and faster code!

[Sana Tayyeb]

this loop is caluculation meanGL. after loop ends i can only access meanGL of last spot .i want to save meanGL of all spots in a way that after calculation i can access meanGL of all spots.

for k = 1 : numberOfSpots           

     thisSpotPixels = SpotMeasurements(k).PixelIdxList;  % Get list of pixels in current blob.     
      meanGL = mean(i(thisSpotPixels)); % Find mean intensity
  end

Thanks in advance

[Debasish Roy]

first of all make a script like this, then run it. You will get your answer i hope.

clear all clc

x = []; y = []; k =[]; f = []; for i= 1:4 fprintf('Enter the temperature of day %d \n' ,i ); s = input(' in celcius '); x(i) = s; y(i) = i; end k = x+273; f = x*9/5 + 32; plot( y, x , '-R', y , f ,'-G' ,y ,k, ' -B')

Answer 1

[Konstantinos Sofos]

x = [] % initialize your matrix/vector

for i=1:10
 % do something useful
 s=a+b
 x = [x,s];
end

[Stephen23]

There are multiple issues with this code:

• no array preallocation: every loop iteration is going to increase the size of the variable x, which means MATLAB has to check if it still fits in the given memory, and move it if it doesn't.
• concatenation instead of indexing: rather than concatenating s onto x with every iteration, it would be better to simply index into x and assign the values of s.
• the name of the loop variable i shadows the inbuilt names of the imaginary unit. Do not use i or j for variable names.

Rather than learning poor code practices like this, you should consider vectorizing the calculation, which is what MATLAB themselves advise for writing fast and neat code, and will expand neatly to larger data sizes.

As a beginner it is better to learn good code practices from the start, rather than learning poor habits and trying to change them later.

[Konstantinos Sofos]

More or less I agree with you...but here we do not have any performance issue question...just a way to keep the values ;)

[hemasai proddutur]

d = 0;

for t=1:10000

d = d+0.1;

end

i want to store the values in array in the loop [0.1 -----------------1000]

Answer 2

[Anil Kumar]

may be helpful for begginers

x1=[];

x2=[];

a=[2 4 6 7 3];

b=[1 9 7 5 8];

for ii=1:5

s=a(ii)+b(ii);

x1=[x1,s];%output in a row

x2=[x2;s];%output in a column

end