Hi, so I'm trying to plot this equation: y=-(sqrt(288-2*x.^4))/x with x=0:0.05:3.267 but y is giving me a single answer (-6.55) and when i do plot(x,y) the graph is empty! Can someone help me please!

Asked by Seamus Pugh

Seamus Pugh (view profile)

on 29 Feb 2016
Latest activity Answered by Jos (10584)

Jos (10584) (view profile)

on 29 Feb 2016
Hi, so I'm trying to plot this equation: y=-(sqrt(288-2*x.^4))/x with x=0:0.05:3.267 but y is giving me a single answer (-6.55) and when i do plot(x,y) the graph is empty! Can someone help me please!

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Ingrid (view profile)

on 29 Feb 2016

you have forgotten to also use the ./ operator instead of the / operator. The code below should give what you try to achieve
x=0:0.05:3.267;
y=-(sqrt(288-2*x.^4))./x;
plot(x,y)

Torsten (view profile)

on 29 Feb 2016

You forgot a dot (.) in front of "/x".
Best wishes
Torsten.

Answer by Jos (10584)

Jos (10584) (view profile)

on 29 Feb 2016

The plot is not empty. It contains 66 points all having the same y value (at y=-6.5514), which can be seen here:
plot(x,y,'bo')
Why is y a scalar? Because, as others told you already, there is a difference between element-wise (.* and ./) and matrix operators (* and /):
x = 1:4
x ./ x
x / x