why won't this plot?

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Don
Don 2016-10-4
评论： Don 2016-10-4
for i = 1:length(xaxis); if xaxis(i) >0; plot(xaxis(i),yaxis(i)); end
end;
xaxis and yaxis have numbers. I always get a blank plot space

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采纳的回答

Steven Lord
Steven Lord 2016-10-4
% Sample data
xaxis = -2*pi:0.1:2*pi;
yaxis = sin(xaxis);
% Determine the points with positive x coordinates and plot them
positiveXAxisMask = xaxis > 0;
plot(xaxis(positiveXAxisMask ), yaxis(positiveXAxisMask ), 'x')
% Let's plot the negative x coordinates as well for illustration
hold on
plot(xaxis(~positiveXAxisMask ), yaxis(~positiveXAxisMask ), 'o')
  1 个评论
Don
Don 2016-10-4
yay! this one worked. I accepted the earlier answers too quickly

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更多回答（3 个）

Massimo Zanetti
Massimo Zanetti 2016-10-4
Yes, because you are plotting just on point. Better try this:
plot(xaxis,yaxis)
Gareth Thomas
Gareth Thomas 2016-10-4
编辑：Gareth Thomas 2016-10-4
You need to add the hold on command. Try this:
for i = 1:length(xaxis); hold on;if xaxis(i) >0; plot(xaxis(i),yaxis(i),'x'); end; end;
Notice the 'x' which helps you see it.
Gareth Thomas
Gareth Thomas 2016-10-4
for i = 1:length(xaxis); hold on ;if xaxis(i) >0; plot(xaxis(i),yaxis(i),'x'); end; end;

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