Could somebody explain the code by Elias Wegert to me?

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Sp00n 2017-10-11

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编辑： Guillaume 2017-10-11

I read some of the book "Visual Complex Functions" by Elias Wegert. In the epilogue, he provides a short Matlab code for plotting phase portraits:

xmin=-0.5; xmax=0.5; ymin=-0.5; ymax=0.5;
xres = 800; yres = 800;
x = linspace(xmin,xmax,xres);
y = linspace(ymin,ymax,yres);
[x,y] = meshgrid(x,y); z = x+1i*y;
f = exp(1./z);
p = surf(real(z), imag(z),0*f, angle(-f));
set(p,'EdgeColor','none');
caxis([-pi,pi]), colormap hsv(600)
view(0,90), axis equal, axis off

Since I'm very new to Matlab, I don't really get everything about it. Especially since there's an error on line 7 for me ("X, Y, Z, and C cannot be complex."). Could somebody explain to me why there's 0*f and angle(-f)? And what can I do to make it work? Thank you in advance.

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Answer 1

Guillaume 2017-10-11

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https://ww2.mathworks.cn/matlabcentral/answers/360753-could-somebody-explain-the-code-by-elias-wegert-to-me#answer_285231

编辑：Guillaume 2017-10-11

在 MATLAB Online 中打开

The error message occurs because some elements of f are Inf + 1i*Inf, which when multiplied by 0 give 0 + 1i*NaN (I would have expected it to give NaN + 1i*NaN)

I assume that the 0*f is just a lazy way to create a zero matrix the same size as f, so you could replace that by zeros(size(f))

p = surf(real(z), imag(z), zeros(size(f)), angle(-f));