plotting one variable function

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danish ansari
danish ansari 2020-12-9
回答： Star Strider 2020-12-9
i want to plot a graph:
y axis: 4/(1+Ri)^2
xaxis: (1+Ri)/(2*(1-Ri)) : it should vary from 2 to 25
Ri is the only variabe.
i tried with both fplot and plot command but both are giving me different plot.
just want to know what is the correct method to plot this.?

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采纳的回答

Walter Roberson
Walter Roberson 2020-12-9
Ran in:
xfun = @(Ri) (1+Ri)./(2*(1-Ri));
yfun = @(Ri) 4./(1+Ri).^2;
zfun = @(Ri) zeros(size(Ri));
h = fplot3(xfun, yfun, zfun, [3/5, 50/51]); view(2); xlim([2 25]); ylim([1 1.6])
The correct upper bound for Ri should be 49/51 but in practice if you use that, fplot3 cuts off at 19 point something.

更多回答（2 个）

Star Strider
Star Strider 2020-12-9
Another approach:
sRi(1) = fsolve(@(Ri) (1+Ri)./(2*(1-Ri)) - 2, 0.01);
sRi(2) = fsolve(@(Ri) (1+Ri)./(2*(1-Ri)) - 25, 0.01);
Ri = linspace(sRi(1), sRi(2));
X = (1+Ri)./(2*(1-Ri));
Y = 4./(1+Ri).^2;
figure
plot(X, Y)
grid
producing:
With ‘X’ going from 2 to 25, as requested.
James Tursa
James Tursa 2020-12-9
Your question is unclear. Is it Ri that varies from 2 to 25? And the y-axis and x-axis formulae you have are the coordinates of (x,y) points for a curve?
Is this what you want:
Ri = 2:0.125:25;
x = (1+Ri) ./ (2*(1-Ri));
y = 4 ./ (1+Ri).^2
plot(x,y);
  1 个评论
danish ansari
danish ansari 2020-12-9
on x axis term ''(1+Ri) ./ (2*(1-Ri))" varying from 2 to 25.
yes those are the coordinates for (x,y) points for a curve.

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