Finding x that approximate y to zero

I am trying to find the the value x that make y approximately zero. Here is what I did:
e= 0.001 %error bar
for x = linspace(100, 170, 1000);
y = 18.9*log(x/170) +0.0042*(x-170) + 8.314*log(0.000267/0.0001413);
end
Thanks in advance.

 Accepted Answer

e= 0.01 %error bar
x = linspace(100, 170, 1000);
y = 18.9*log(x/170) +0.0042*(x-170) + 8.314*log(0.000267/0.0001413);
idx=find(abs(y)<e)

4 Comments

Thank you for your quick response. That really helped me, but I want to know the value of X. like what value of x between this range( 100 to 170) that make Y approximately equal to zero. Thank you though for your time.
If you are looking for the nearest value to 0.
e= 0.01 %error bar
x = linspace(100, 170, 1000);
y = 18.9*log(x/170) +0.0042*(x-170) + 8.314*log(0.000267/0.0001413);
[max_val,index_val]=min(abs(y))
Thank you! Much Appreciated!

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More Answers (1)

Consider
x0 = fzero( @(x) 18.9*log(x/170) +0.0042*(x-170) + 8.314*log(0.000267/0.0001413), [100, 170]);

1 Comment

Thank you Walter! That's indeed a faster way! Much Appreciated! You Rock!

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