intersction graph with line
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Hi everyone, can u help me out im still pretty green. This is a simple one but I cant figure it out. I tried to look for similar problem but did not find satisfy answer.
I'm having some data set which I plot with basic plot command. My question is, can matlab give me right away answer for the y value at my distance of say 4.5 like in the simplify example having in mind that my graph is just a line connecting y values
x=1:10;
y=-5*rand(1,10);
plot(x,y)
hold on
plot([4.5 4.5],[0 -5],'r')
thanks in advance.
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Star Strider
2012-8-30
编辑：Star Strider
2012-8-30
I am not exactly certain what you want, but my guess would be:
p = polyfit(x,y,1);
y1 = polyval(p, 4.5);
The value returned for y1 would then be the value that might be expected to be at an x value of 4.5 on that particular iteration based on a linear fit. Since your data are changing between iterations (they are random), y1 will change with them.
If you want to know what the value is on a line between connecting points, to calculate the value for 4.5, the easiest way is probably:
p = polyfit([4 5], y([4 5]), 1);
y1 = polyval(p, 4.5);
That is how I would do it.
(And thank you Walter for your editing.)
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Star Strider
2012-8-31
It is my pleasure to help!
I do not know what your data look like so I cannot suggest a specific solution that might work for you in all situations. However, I suggest you also look at MATLAB's various interpolation functions, for example interp1, and more generally, the functions in Interpolation and Computational Geometry.
Thank you for accepting my answer.
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