Displaying non existant array elements

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Ali Kiral
Ali Kiral on 8 Mar 2025
Edited: dpb on 8 Mar 2025
Why am I getting repeating numbers for the array x as an output for the following piece of script?
x=1:0.5:5;
for i=1:length(x);
y(i)=x(i)^2;
end
fprintf(' x y\n')
x y
Results=[x;y];
fprintf('%10.0f %38.16f\n', Results);
1 1.0000000000000000 2 2.2500000000000000 2 4.0000000000000000 2 6.2500000000000000 3 9.0000000000000000 4 12.2500000000000000 4 16.0000000000000000 4 20.2500000000000000 5 25.0000000000000000
  1 Comment
Stephen23
Stephen23 on 8 Mar 2025

“Why am I getting repeating numbers for the array x as an output for the following piece of script?”

You are not getting the same values repeating in x. You just confused how values are displayed with the values stored in memory. Try printing the values of x with e.g. two decimal places. Then tell us what you see.

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Accepted Answer

dpb
dpb on 8 Mar 2025
Moved: dpb on 8 Mar 2025
x=1:0.5:5;
for i=1:length(x);
y(i)=x(i)^2;
end
fprintf(' x y\n')
x y
Results=[x;y];
fprintf('%10.2f %38.2f\n', Results);
1.00 1.00 1.50 2.25 2.00 4.00 2.50 6.25 3.00 9.00 3.50 12.25 4.00 16.00 4.50 20.25 5.00 25.00
Because the '%10.0f' required rounding the x values to display integer values...
  2 Comments
dpb
dpb on 8 Mar 2025
Edited: dpb on 8 Mar 2025
No problem...as @Stephen23 notes directly and my response says same thing indirectly, you have to remember the difference between what the variable value and its representation may be.
BTW, you do recognize that with MATLAB array syntax you can eliminate the need for the for...end loop in the above, right?
x=1:0.5:5;
y=x.^2;
Results=[x;y];
fprintf('%10s%38s\n','x','y')
x y
fprintf('%10.2f %38.2f\n', Results);
1.00 1.00 1.50 2.25 2.00 4.00 2.50 6.25 3.00 9.00 3.50 12.25 4.00 16.00 4.50 20.25 5.00 25.00
NOTA BENE the "dot operator" on the expnentiation power, .^: to indicate element-wise operations rather than mpower, ^: which is matrix exponentiation..

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