Recently I have come across usage of cluster plot, which combines k-mean clustering along with PCA. The plot shows different clusters plotted using first two PCs. I have checked some of the threads (here and here) regarding the usage.
I want to know, during generating a cluster plot, does the data is clustered first and then PCA is done, or the reverse way (PCA followed by k-mean clustering)?
Because the second link says PCA is done followed clustering. But in the first link where an example is shown to generate a cluster plot, data is clustered first and then the cluster plot is generated.
Regarding interpretation, does the plot has to be interpreted as the number of clusters generated or are there any extra points to interpret?