How to plot a line over a specific interval?

Question

Alexander Horton 2020-6-29

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https://ww2.mathworks.cn/matlabcentral/answers/556879-how-to-plot-a-line-over-a-specific-interval

评论： Alexander Horton 2020-6-30

I am attempting to plot cubic splines for 5 points. I have 4 functions to match each segment, but I only want the interval of the line that applies to that segment to appear on my plot.

I have these four lines:

plot (x,g(1))

plot (x, g(2))

plot(x, g(3))

plot(x, g(4))

They appear as so:

This is correct, but i want g1 to ONLY show from -1 to -.5. g2 to ONLY show from -.5 to 0, etc.

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Answer 1

the cyclist 2020-6-29

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https://ww2.mathworks.cn/matlabcentral/answers/556879-how-to-plot-a-line-over-a-specific-interval#answer_458773

编辑：the cyclist 2020-6-29

在 MATLAB Online 中打开

Can you upload the data? Specifically, it is unclear to me what sort of data type g is.

Instead of plotting x, you'll want to do something like plotting

x(x>-1 & x<-0.5); % for g1

but I can't tell how to handle g1 without more info.

Also, it was unclear to me if the intervals are meant to be on x, or on g.

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the cyclist 2020-6-29

Yes, I edited it. Thanks.

Alexander Horton 2020-6-30

I ended up figuring everything out. I ended up using fplot, which let me put in an interval to show as an input.

fplot (@(x) (a(2).*(x-z(2)).^3+b(2).*(x-z(2)).^2+c(2).*(x-z(2))+d(2)), [-1 -.5], '-.r','linewidth',2);

Im sure this isnt the most efficient way but it got the job done haha.

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Answer 2

madhan ravi 2020-6-29

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ix = (g1 >= -1) & (g1 <= -.5); % follow the same for the rest
plot(x(ix), g1(ix))

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the cyclist 2020-6-29

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The fact that OP wrote

g(1)

rather than

g1

made me hesitate to suggest this solution. We'll see.

madhan ravi 2020-6-29

Haha me too , I hate suspenses xD.

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