4
$\begingroup$

When using StreamPlot with two different ranges, one gives a plot artifact and it is not clear what it is trying to say.

If you plot

  StreamPlot[{1, (-x + x^2 + y^2)/(x^2*y*(-1 + x*y))}, {x, -2, 2}, {y, -2, 2}]

The plot is

correct plot with streams

If you slightly change the range

 StreamPlot[{1, (-x + x^2 + y^2)/(x^2*y*(-1 + x*y))}, {x, -1.64028, 1.71557}, {y, -1.64028, 1.71557}]

The plot is

similar plot, but contains an upwards pointing red arrow where a downwards blue one was before close to the center of the plot

What does the item circled in red represent? Is it just some unwanted artifact? Why is it a different color?

$\endgroup$

1 Answer 1

3
$\begingroup$

Set y->0.1 and draw the y component of the corresponding vector as a function of x:

Plot[(-x + x^2 + y^2)/(x^2*y*(-1 + x*y)) /. y -> 0.1, {x, -1, 1}]

enter image description here

You see that the y-component at the point x==0 is very small. And this is what the different color of the vector communicates.

$\endgroup$
2
  • $\begingroup$ Hmm - so is this showing that artifact StreamPlot[{1, (-x + x^2 + y^2)/(x^2* y*(-1 + x*y))}, {x, -.1, .1}, {y, -.5, .5}]? $\endgroup$
    – Moo
    Jul 14, 2022 at 16:08
  • 2
    $\begingroup$ It is not an artifact it is the color function. $\endgroup$ Jul 14, 2022 at 16:12

Your Answer

By clicking “Post Your Answer”, you agree to our terms of service and acknowledge you have read our privacy policy.

Not the answer you're looking for? Browse other questions tagged or ask your own question.