plotting one variable function

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.?

Answer 1

[Walter Roberson]

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.

[danish ansari]

It helps.

Thanks you very much Walter Roberson.

Answer 2

[Star Strider]

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.

Answer 3

[James Tursa]

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);

[danish ansari]

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.