The problem of For+RegionPlot

Question

I type the following code in Mathematica 11:

For[n = 1, n <= 3, n++,
 RegionPlot[x^2 + y^3 < n, {x, -2, 2}, {y, -2, 2}]
]

Then I press Shift+Enter, but Mathematica does not output any figures. Where is the problem? Thanks in advance.

This is a common mistake for users new to Mathematica, or coming from earlier versions. Plots return Graphics expressions rather than displaying them as side-effects. See (47123). You could add Print but generally a better method is to replace For with Table: Table[RegionPlot[x^2 + y^3 < n, {x, -2, 2}, {y, -2, 2}], {n, 1, 3}]. You can further format that output with Column or GraphicsColumn as desired, or animate it with ListAnimate. — Mr.Wizard, Aug 16 '16 at 08:24
Note: does there exist a canonical Q&A on this issue? If not I think a post should be made in (18393) regarding this, as it has come up quite often. — Mr.Wizard, Aug 16 '16 at 08:28

score 5 · Accepted Answer · edited Apr 13 '17 at 12:55

5

It depends on what your aim. If it is just to 'print' 3 graphics:

For[n = 1, n <= 3, n++, 
 Print@RegionPlot[x^2 + y^3 < n, {x, -2, 2}, {y, -2, 2}]]

If you want an object you can use and refer to:

f[x_, y_] := x^2 + y^3
rps=RegionPlot[f[x, y] < #, {x, -2, 2}, {y, -2, 2}] & /@ Range[3]

This is also a useful link with respect to loops in Mathematica.

edited Apr 13 '17 at 12:55

Community

answered Aug 16 '16 at 08:24

ubpdqn

ubpdqn: Thank you for your answer. – Wei-Cheng Liu Aug 16 '16 at 08:32
@Wei-ChengLiu you're welcome. I had exactly the same question when I first started using Mma. Have fun:) – ubpdqn Aug 16 '16 at 08:34
Surely in this case Table[]>For[] – Feyre Aug 16 '16 at 09:53
2

@Feyre as you and Mr.Wizard have suggested Table may be natural alternative. I provided link to motivate looking at alternatives. – ubpdqn Aug 16 '16 at 09:57
@Feyre & ubpdqn Thank you for your comments. – Wei-Cheng Liu Aug 16 '16 at 11:53

score 2 · Answer 2 · answered Aug 16 '16 at 08:25

2

For fun

Example

Manipulate[
 RegionPlot[x^2 + y^3 < n, {x, -2, 2}, {y, -2, 2}],
 {n, 1, 3, 1}
 ]

answered Aug 16 '16 at 08:25

e.doroskevic