# Plot {(x,y,z)| x²+y²<1, 0<z<x+2}

4 views (last 30 days)
Eileen Lassler on 10 Feb 2021
Answered: Rik on 10 Feb 2021
I'm not sure abot the code, because of the 2 constraints. I hope someone can help me.

It depends on what you want. One way to code this would be to define your space, i.e. the range of each of each variable, say x goes from -5 to 5 in steps of 0.1:
x=-5:-.1:5;
and the same for y and z. Then x^2 + y^2 < 1 becomes a condition, those points below 1 could be selected and those above discarded, then you do the same with the second condition and your answer could be a cloud of points where the two conditions intersect.

Rik on 10 Feb 2021
Same general idea as @Constantino Carlos Reyes-Aldasoro, but more in steps.
Use linspace or colons to create one or three vectors to define your coordinate grid.
Then you can use ndgrid or meshgrid to expand that/those vector(s) to a full grid.
Now use element-wise operations (.* and ./ and .^) to compute . The logical operators < and > will work element-wise by default.
Now you have logical arrays where the combination of x,y,z is either valid or invalid. You can use logical indexing to either remove them, or mark a value array with NaN.
Now you have x y and z vectors, which you can input to a function like plot3 to show the pointcloid.