How to give different colour for those indices which is zero in matlab plot

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POKA 2017-7-29

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评论： POKA 2017-7-30

采纳的回答： Image Analyst

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Hi All,

I am plotting numerical sensor data from huge file. I got my plot. But I want to show red colour to those points which is zero in the plot. I mean these data are wrong data and I want to give them different colur in the plot.

I tried with

idx=find(not(input5(:,1)));

But it will plot total zeros in the plot.How Can I rectify it. Thanks

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Image Analyst 2017-7-30

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POKA, try this:

y = rand(1, 50) - 0.3;
x = 1 : length(y);
% clip some points to zero
y(y < 0) = 0;
% Find indexes above 0
aboveZero = y > 0;
% Plot all data.
plot(x, y, 'b*-', 'LineWidth', 2);
hold on;
grid on;
% Plot all data zero as red spots.
plot(x(~aboveZero), y(~aboveZero), 'r.', 'MarkerSize', 30);
xlabel('x', 'FontSize', 30);
ylabel('y', 'FontSize', 30);
title('Bad Data in Red', 'FontSize', 30);

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Image Analyst 2017-7-30

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Ignore the first few lines where I had to create my own data because you initially forgot to attach yours:

y = rand(1, 50) - 0.3;
x = 1 : length(y);
% clip some points to zero
y(y < 0) = 0;

I had to have some data for the demo right? And I didn't have your data so I made up some. Since you already have the y data, you can just pick up with the line of code after those.

POKA 2017-7-30

Thanks understood .

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David Goodmanson 2017-7-30

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编辑：David Goodmanson 2017-7-30

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Hi POKA,

something like this?

x = 0:.01:50;
y = sin(x);
ind = abs(y)<.005   % or whatever tolerance is appropriate to find the zeros;
                    % sometimes y == 0 will not work
plot(x,y,x(ind),y(ind),'.r')