Hi my friends,

I'm trying to make a scatterplot like this.

1) I have a 3-variable dataset.  They are ID, x, and y.

2) "x" is for the X-axis, "y" for the Y-axis, and "ID" is used to label all
the cases in the scatterplot.

3) After creating the scatterplot, I need to add both a X-axis  reference
line and a Y-axis reference line.  The X-axis reference line is a vertical
line starting from the center of the X-axis.  The Y-axis reference line is a
horizontal line starting from the center of the Y-axis.  In other words, by
creating the two reference lines, the scatterplot is divided into 4
quadrants.

Please help me figure out how to do that in R.

Many thanks in advance!

Feng

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