How do I show a quiver plot from a matrix?
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I am trying to graph this direction field:
x' = (1 1; 4 1)x
This is my code:
a = [1 1;4 1];
x = [x y];
[x,y] = meshgrid(-10:1:10,-10:1:10);
dx = 1;
dy = a.*x.*1;
r = ( dx.^2 + dy.^2 ).^0.5;
u = dx./r;
v = dy./r;
figure
quiver(x,y,u,v);
It returns this error:
ꕋerror: QuiverPlot: product: nonconformant arguments (op1 is 2x2, op2 is 21x21)
error: called from
QuiverPlot at line 5 column 4
I guess my x vector does not have the same dimension as my a vector, even though a has two columns and x has two rows.
As a side note, this problem was given by Boyce and Diprima's textbook with no context regarding the code.
1 个评论
Dylan Voss
2020-7-14
编辑：Cris LaPierre
2020-7-14
回答（1 个）
Cris LaPierre
2020-7-14
0 个投票
The issue is with your calculation of dy. Variable a is 2x2, but t is 42x21.
2 个评论
Dylan Voss
2020-7-19
Cris LaPierre
2020-7-20
编辑：Cris LaPierre
2020-7-20
Because you create it using x and y, specifically placing y directly underneath x, and they are each 21x21. Perhaps take a look at the documentation for meshgrid.
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2020-7-14
2020-7-20
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