Regression line does not show on scatterplot

Hello,

I have done a scatterplot and now would like to add its regression
line but it does not show.
Below, the code I have used. 

lm3 <- lm(data$S_pH_KCl2.5_BCx~data$B_OleicoPF_BCx_per)
plot(data$S_pH_KCl2.5_BCx, data$B_OleicoPF_BCx_per)
abline(lm3)

I have been able to do the complete operation using the software
STATISTICA but it would be great to do it with R.

If you require more details please get in touch.

Thanks a lot!
Bea

By the look of things you have either the regression or the plot
the wrong way round. I suspect it is the regression. So try:

Either:
##lm3 <- lm(data$S_pH_KCl2.5_BCx~data$B_OleicoPF_BCx_per)
  lm3 <- lm(data$S_pH_KCl2.5_BCx_per~data$B_OleicoPF_BCx)
  plot(data$S_pH_KCl2.5_BCx, data$B_OleicoPF_BCx_per)
  abline(lm3)

Or:
  lm3 <- lm(data$S_pH_KCl2.5_BCx~data$B_OleicoPF_BCx_per)
##plot(data$S_pH_KCl2.5_BCx, data$B_OleicoPF_BCx_per)
  plot(data$S_pH_KCl2.5_BCx_per, data$B_OleicoPF_BCx)
  abline(lm3)

The point is that in lm(V~U) the variable "U" is taken as
corresponding the the x-axis (independent variable), and the
variable "V" to the y-axis (dependent variable).

Similarly for plot(U,V).

So, for lm3 <- lm(V~U), abline(lm3) will plot the fitted V-values
(y-axis) against the U-values (x-axis).

Your original code was equivalent to:

  lm3 <- lm(V~U)
  plot(V,U)
  abline(lm3)

whereas it should be
Either:
  lm3 <- lm(V~U)
  plot(U,V)
  abline(lm3)
Or:
  lm3 <- lm(U~V)
  plot(V,U)
  abline(lm3)

Hoping this helps,
Ted.

-------------------------------------------------
E-Mail: (Ted Harding) <Ted.Harding at wlandres.net>
Date: 18-Dec-2012  Time: 21:00:25
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