Why the imaginary part of the points p1,p2,p3 isn't zero in the plane?

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Giuseppe Alfieri 2018-7-16

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评论： Giuseppe Alfieri 2018-7-16

采纳的回答： Steven Lord

p1=1;

p2=3;

p3=4;

plot([p1,p2,p3],'x')

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Answer 1

Steven Lord 2018-7-16

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When called with one data input, the plot function behaves differently depending on whether that data input is real or complex. From the documentation:

"plot(Y) creates a 2-D line plot of the data in Y versus the index of each value.

If Y is a vector, then the x-axis scale ranges from 1 to length(Y).

...

If Y is complex, then the plot function plots the imaginary part of Y versus the real part of Y, such that plot(Y) is equivalent to plot(real(Y),imag(Y))."

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Giuseppe Alfieri 2018-7-16

So i have to write for example p1=1+0×i; as real part and imaginary part is it correct?

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Answer 2

Jesus Sanchez 2018-7-16

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You are not plotting a Real vs Imag plot, but just the normal one. The 'x' makes the plotted data to be represented as an x marker, but that is all. When you execute that code, MATLAB shows the corresponding value in y-axis and the index of that value in x-axis. That is why your first value appears in the position "1" in x-axis, your second in "2" etc etc