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Marker indices for a plot error

35 vues (au cours des 30 derniers jours)
Robert Scott
Robert Scott le 15 Août 2021
Commenté : Star Strider le 15 Août 2021
So for whatever reason matlab will not allow me to make a marker index of less then 1. I get an error of
"Value must be a vector of positive integers."
I dont understand the problem. The plot has an x axis scale of very small numbers like .00001-.0001
So naturally my markers must be in that range.
Does anyone know why im getting this error?
  1 commentaire
Robert Scott
Robert Scott le 15 Août 2021
If i make the marker index 1 the error goes away.

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Réponses (2)

the cyclist
the cyclist le 15 Août 2021
The MarkerIndices Name-Value pair is expecting the indices of the data points (e.g. the 1st, 5th, and 10th data point) to place the markers, not the values of those data points.
You might want to use the XTick property of the axes instead.
  1 commentaire
Robert Scott
Robert Scott le 15 Août 2021
This is just rediculous.
Now xticks is telling me the indices must be increasing.
Who cares if they are increasing. All i want to do is put a "dot" on a point on a plot.
when thigns like min and max come back i have no idea if one index will be greater then the other.
Mathworks needs to significantly rethink the constraints on some of these elementry functions.

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Star Strider
Star Strider le 15 Août 2021
From the documentation on MarkerIndices:
Indices of data points at which to display markers, specified as a vector of positive integers
and 0.01 is not an integer.
  4 commentaires
Robert Scott
Robert Scott le 15 Août 2021
Modifié(e) : Robert Scott le 15 Août 2021
and that is the issue, i dont know the index, i just no the x location I cant figure it out because the numbers im working with are very very small and im having a tuff time with truncating to do the math to figure out the actual index.
All i want to do is plot a point on a graph with an absolute X value and absolute y value
I also have tried to use create an x and y vector of the points i want to put a marker and plot that seperate but the issue is when i use plot twice once for the line and then again for the markers it overwrites it even with hold on
Your plot above works because you know the index.
I do not, i only know the absolute time
Star Strider
Star Strider le 15 Août 2021
In that situation, and you want to put it at a x-value of 0.01, use interp1 and tthe x-values to find the y-values for the markers —
x = -0.5:0.13:2.5;
y = (x-1).^2;
plot(x, y)
xp = 0.01;
yp = interp1(x, y, xp);
hold on
hp = plot(xp, yp, 'p');
hold off
hp.MarkerSize = 10;
hp.MarkerFaceColor = 'g';
If you have the y-values and want to find the x-values, this becomes a bit more complicated, however otherwise straightforward.

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