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how to plot data points with different color in scatter plot?

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Lei
Lei on 24 May 2012
hello,everyone. I have a very large matrix, thousands of rows and 15 columns. Now i wanna analyze four variables(columns). I used the scatter plot for plotting each of the two variables. My question is how can I plot different colors for different groups of data in scatter plot. I wrote a if statement but its very slow, so I am wondering anyone have any better ways to do it.
for i=1: length(PaskapooFm4(:,14));
if PaskapooFm4(i,14)==1
scatter(PaskapooFm4(i,3),PaskapooFm4(i,12),'.b');hold on;
elseif PaskapooFm4(i,14)==2
scatter(PaskapooFm4(i,3),PaskapooFm4(i,12),'.g');hold on;
elseif PaskapooFm4(i,14)==3
scatter(PaskapooFm4(i,3),PaskapooFm4(i,12),'.r');hold on;
elseif PaskapooFm4(i,14)==4
scatter(PaskapooFm4(i,3),PaskapooFm4(i,12),'.c');hold on;
elseif PaskapooFm4(i,14)==5
scatter(PaskapooFm4(i,3),PaskapooFm4(i,12),'.m');hold on;
elseif PaskapooFm4(i,14)==6
scatter(PaskapooFm4(i,3),PaskapooFm4(i,12),'.y');hold on;
elseif PaskapooFm4(i,14)==7
scatter(PaskapooFm4(i,3),PaskapooFm4(i,12),'.b');hold on;
elseif PaskapooFm4(i,14)==8
scatter(PaskapooFm4(i,3),PaskapooFm4(i,12),'h');hold on;
elseif PaskapooFm4(i,14)==9
scatter(PaskapooFm4(i,3),PaskapooFm4(i,12),'>');hold on;
elseif PaskapooFm4(i,14)==10
scatter(PaskapooFm4(i,3),PaskapooFm4(i,12),'<');hold on;
end
xlabel('GAMMA(API)');ylabel('RES(DG)(OHM-M)');
title('Crossplot of Gamma and RESD')
end
the above code used to plot two variables (column 3 and column 12), and each row is in 10 categories as indicated by column 14. Column 14 are just numbers: 1 to 10. So what i did here is using scatter plot for plotting the two varibales and assign different color for each number( 1 to 10). However, this is very slow and the code is long. Anybody could think of a better way? Many thanks! BTW, I also need to figure out those 4 variables' relationship. How can I fit a best line to the scatter plot? because there are so man different ones(liner,quadratic,third order...). I mean how can I decide which one is the best fit. Or any other better ways to visualize multidimensional data? I tried to use plotmatrix,pca. etc....
  2 Comments
Lei
Lei on 24 May 2012
Hi oleg,I did!
But i am not sure about the meaning of group in gscatter cauz I have created my own group,which is column 14 (number 1 to number 10),i.e., 10 different groups. I thought my group is different from the group in gscatter, am I right? I am not sure about this

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Answers (1)

Patrick Kalita
Patrick Kalita on 24 May 2012
You can use the fourth input argument to scatter to control the color of each marker in the scatter plot. For example:
scatter(PaskapooFm4(:,3), PaskapooFm4(:,12), [], PaskapooFm4(:,14));
Note that it will only change the color of the marker, not the shape of the marker.

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