How do I label the points in a multidimensional scaling plot?

I am studying how to do multidimensional scaling in matlab. I am able to reproduce the output (2D plot) from a published example (http://www.sthda.com/english/articles/31-principal-component-methods-in-r-practical-guide/122-multidimensional-scaling-essentials-algorithms-and-r-code/).

The output is based on the data table found in the Swiss Fertility and Socioeconomic Indicators (1888) (https://rpubs.com/krishnakuyate/Swiss_FS_Data).

I constructed a 47x47 array of Euclidean distances (D) of the Swiss Fertility and Socioeconomic Indicators and ran Y=cmdscale(D,2) to obtain a plot of these data:

My plot looks very similar (but inverted mirror image) to the published plot from http://www.sthda.com/english/articles/31-principal-component-methods-in-r-practical-guide/122-multidimensional-scaling-essentials-algorithms-and-r-code/:

But how can I get matlab to label the points in my plot as is done above in the published figure?

Answer 1

[Andres Adam]

Hi Stephen, check out the first example in the documentation of cmdscale:

https://www.mathworks.com/help/stats/cmdscale.html

There is no direct option in cmdscale to add text, but we can do so by using the function text, with the point coordinates offset by a little bit, and a cell array of names:

plot(Y(:,1),Y(:,2),'o') % Your plot
text(Y(:,1)+25,Y(:,2),names)

where the variable names is something like

>> names = {'Herens', 'Sierre', 'Conthey', ... }; (in the appropriate order!)

[Stephen]

Thanks Andres! Yes, that works but I came across a workaround that is a bit easier for me. Namely, I create a cell array "names" with names copy/pasted from the parent data table:

names=cell(n,1)      % n = number of names

Then after I generate the multidimensional scalng 2D plot I run

gname(names);

This allows me to place names on indivividual data points by moving the "crosshairs" that appear on the plot ofer that data point and clicking.

I'll try working with both methods to see which is faster for me.

[Andres Adam]

I did not know that feature! Thanks for pointing it out, and be careful to not confuse points when labeling manually :)