Trouble with my function
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I want to run this code:
syms x
syms y(x)
y(x) = 5*(x^2);
values = 4;
h = 1;
derivative(5,1)
function yd = derivative(values, h)
syms y(x)
yd = (y(values + h) - y(values - h)) / (2*h);
end
But instead of getting the real value ( in this case 40 ), I got :
ans =
y(6)/2 - y(4)/2
How can I solve this please.
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Answers (1)
Star Strider
on 9 Jan 2021
You need to tell your ‘derivative’ function what ‘y’ is.
Changing ‘derivative’ to an anonymous function (for my convenience) and otherwise leaving it unchanged (except to add ‘y’ as an argument):
syms x y(x)
derivative = @(values, h, y) (y(values + h) - y(values - h)) / (2*h);
y(x) = 5*(x^2);
values = 4;
h = 1;
Result = derivative(5,1,y)
produces:
Result =
50
Note —
Check = diff(y)
CheckTest = Check(values)
produces:
CheckTest =
40
I will let you troubleshoot that discrepancy.
6 Comments
Star Strider
on 9 Jan 2021
I am not getting any error messages when I run the code I posted.
You need to include ‘y’ as an argument in your call to it. Currently, you are not doing that. See my original Answer in order to unbderstand how to do that correctly.
Other than that, I have no idea what the problem is with your implementation of it.
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