R help - Dec 2007 - lm: how to calculate rsquared of the predicted values?

Hi,

I've built a linear model using multiple linear regression which leads me a
R-squared value of 73.58%.

After that, I used this model to predicted some values based on the test
data.
Now I'm wondering how:

1.  can I measure de R-squared value between the predicted(by the model) and
real (observed) values.?
2. Measure the RMSE error .

Example: suppose my data its below:

REAL  Predicted
8.22     9.016811
28.24     9.016811
29.69    26.491108
78.02    59.234736
51.29    67.823793
37.55    18.033622
10.82    29.683154


-- 
Thanks in advance,

Giovane

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>
> 1.  can I measure de R-squared value between the predicted(by the model)
and
> real (observed) values.?
> 2. Measure the RMSE error .
>
There is a function in the caret package called postResample that will
do that (even if you aren't using resampling).

As has been previously noted on this list, there are a number of
formulas for R-squared. This function uses the square of the
correlation between the observed and predicted. The next version of
caret will offer a choice of formulas.

-- 

Max