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# 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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Seamus Pugh on 29 Feb 2016
Closed: MATLAB Answer Bot on 20 Aug 2021
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!

Ingrid 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 on 29 Feb 2016
You forgot a dot (.) in front of "/x".
Best wishes
Torsten.

Jos (10584) 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