I'm using corrplot in R to plot the correlation matrrix. For some reason, the edges of the circles in the plot seems missing some pixels. The plot overall looks very rough. Please see the graph I plotted:
But the example I followed shows the plot is supposed to be like this:
My initial guess was dpi and scaling issue because I use a 4K display. I tried changing the resolution and size of the plots but it doesn't work.
Thank you so much for your help.