How to plot a nonlinear equation in matlab

Question

I need to plot this equation : (y)/[(4*3.14*10^-7)*(1+(4200/(1+0.03(y^8.2))^0.5))] on the interval y=0 to y=3

I tried this

y=0:0.5:1:1.5:2:2.5:3;
x=(y)./((4*3.14*10.^-7)*(1+(4200./(1+0.03*y.^8.2).^0.5)));
plot(x,y)

Answer 1

Your plot is fine, only your y is defined problematically: the syntax is var=from:step:to , no additional colons needed. So you either say

y=[0 0.5 1 1.5 2 2.5 3];

or, what's much better,

y=0:0.5:3;

or, what's equivalent now,

y=linspace(0,3,7);

Note that the last form will make it easy for you to produce a finer graph of your function (since plot by default will draw you a piecewise linear function, ie connect the points with line segments). So you might want to increase the number of points from 7 to something larger, like 50 .

NO wait, there's also a slight problem: you should have .* instead of * in the definition of x , like every other operation is also prepended with a . (to make those operations element-wise array operations).

AND you have to plot(y,x) as that seems to be the order of your function: y is independent and x is the value of the function.

Fixed version:

y=linspace(0,3,50);
x=(y)./((4*3.14*10.^-7).*(1+(4200./(1+0.03*y.^8.2).^0.5)));
plot(y,x)
xlabel('y')
ylabel('x(y)'); %for clarity

Result: