Control the size of points in an R scatterplot

Question

In R  the plot   function takes a pch argument that controls the appearance of the points in the plot   I m making scatterplots with tens of thousands of points and prefer a small  but not too small dot   Basically  I find pch     to be too small  but pch 19 to be too fat   Is there something in the middle or some way to scale the dots down somehow

User · Answer

pch 20 returns a symbol sized between     and 19    It s a filled symbol  which is probably what you want    Aside from that  even the base graphics system in R allows a user fine-grained control over symbol size  color  and shape  E g    dfx   data frame ev1 1 10  ev2 sample 10 99  10   ev3 10 1   with dfx  symbols x ev1  y ev2  circles ev3  inches 1 3                    ann F  bg  steelblue2   fg NULL

User · Answer

As rcs stated  cex will do the job in base graphics package  I reckon that you re not willing to do your graph in ggplot2 but if you do  there s a size aesthetic attribute  that you can easily control  ggplot2 has user-friendly function arguments  instead of typing cex  character expansion   in ggplot2 you can type e g  size   2 and you ll get 2mm point    Here s the example       base graphics     plot mpg   hp  data   mtcars  pch   16  cex    9       ggplot2       with qplot   qplot mpg  hp  data   mtcars  size   I 2     or with ggplot     geom point   ggplot mtcars  aes mpg  hp   size   2    geom point     or another solution  ggplot mtcars  aes mpg  hp     geom point size   2

User · Answer

Try the cex argument    par   cex A numerical value giving the amount by which plotting text and symbols should be magnified relative to the default  Note that some graphics functions such as plot default have an argument of this name which multiplies this graphical parameter  and some functions such as points accept a vector of values which are recycled  Other uses will take just the first value if a vector of length greater than one is supplied

[r] Control the size of points in an R scatterplot?

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