# How can I ask Matlab to adjust a parameter in an equation until the answer becomes equal with a predetermined input value?

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Lewis Tamuno-Ibuomi on 24 Nov 2021
Edited: Stephen23 on 25 Nov 2021
I am trying to compare two heights, a trial and calculated. The trial height of the object is an input to the program, while the program calculates the actual height but I want matlab to compare the both heights by adjusting a parameter in the height equation until both heights become equal. Then, matlab prints the final value of the parameter adjusted in the height equation. Please, can anybody help as I am a novice with very weak programming skills? Thank you.
I don't have any working code as I am still learning from this community hub.
Lewis is my name, a student
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Lewis Tamuno-Ibuomi on 25 Nov 2021
Alright, the height calculation has an equation: h = V/A (volume/area), where V is fixed but A is varied from a range of values. So, an arbitrary input (trial height, ht) is provided for the programe so that matlab could pick the actual value of A from the range of values that will make h = ht. So, the programme is to search out the actual value of A (area) for any ht given that will make h = ht, and print the correct value of A. Thanks Oliver.

Stephen23 on 25 Nov 2021
Edited: Stephen23 on 25 Nov 2021
Define a simple anonymous function with one input which calculates the difference between your two heights, and supply that function as the first input to FZERO. FZERO will adjust that input until the output (i.e. difference) is zero, exactly as you request.
V = 23;
ht = 5;
fh = @(A) ht - V./A;
A = fzero(fh,[0.2,100])
A = 4.6000
V./A
ans = 5
Lewis Tamuno-Ibuomi on 25 Nov 2021
Thank you very much Stephen. I see now!! Really appreciate this quick response. It works very well!

### More Answers (1)

HWIK on 25 Nov 2021
I'm not sure I quite understand the description but here is my go at it:
function Actual_area = call_it_what_you_want(V,ht,Areas)
[~,idx] = min(abs(ht-V./Areas));
Actual_area = Areas(idx);
end
This will take the value of A that gives the closest height to the value of ht
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Stephen23 on 25 Nov 2021
Lewis Tamuno-Ibuomi's incorrectly posted "Answer" moved here:
Thank you Oliver. Did you try any demonstration to test the codes? I would not mind a rough demonstration. Thanks.