R-squared values were added to the plot

How to call R-squared values from lm's?

如何调用线性回归中的R平方值，并将其加到图上呢？

调用数据，观察一下数据

attach(cars)
cars

##    speed dist
## 1      4    2
## 2      4   10
## 3      7    4
## 4      7   22
## 5      8   16
## 6      9   10
## 7     10   18
## 8     10   26
## 9     10   34
## 10    11   17
## 11    11   28
## 12    12   14
## 13    12   20
## 14    12   24
## 15    12   28
## 16    13   26
## 17    13   34
## 18    13   34
## 19    13   46
## 20    14   26
## 21    14   36
## 22    14   60
## 23    14   80
## 24    15   20
## 25    15   26
## 26    15   54
## 27    16   32
## 28    16   40
## 29    17   32
## 30    17   40
## 31    17   50
## 32    18   42
## 33    18   56
## 34    18   76
## 35    18   84
## 36    19   36
## 37    19   46
## 38    19   68
## 39    20   32
## 40    20   48
## 41    20   52
## 42    20   56
## 43    20   64
## 44    22   66
## 45    23   54
## 46    24   70
## 47    24   92
## 48    24   93
## 49    24  120
## 50    25   85

summary(cars)

##      speed           dist    
##  Min.   : 4.0   Min.   :  2  
##  1st Qu.:12.0   1st Qu.: 26  
##  Median :15.0   Median : 36  
##  Mean   :15.4   Mean   : 43  
##  3rd Qu.:19.0   3rd Qu.: 56  
##  Max.   :25.0   Max.   :120

对数据做线性回归(lm)

car <- lm(dist ~ speed)

做图，并在图上加R-squared值

plot(cars)
abline(car)
text(10, 100, as.expression(substitute(italic(R)^2 == r, list(r = round(summary(car)$r.squared, 
    3)))))

总结一下线性回归后的数据，看一下其中的R方(Multiple R-squared)及调整的R方(Adjusted R-squared)

summary(car)

## 
## Call:
## lm(formula = dist ~ speed)
## 
## Residuals:
##    Min     1Q Median     3Q    Max 
## -29.07  -9.53  -2.27   9.21  43.20 
## 
## Coefficients:
##             Estimate Std. Error t value Pr(>|t|)    
## (Intercept)  -17.579      6.758   -2.60    0.012 *  
## speed          3.932      0.416    9.46  1.5e-12 ***
## ---
## Signif. codes:  0 '***' 0.001 '**' 0.01 '*' 0.05 '.' 0.1 ' ' 1
## 
## Residual standard error: 15.4 on 48 degrees of freedom
## Multiple R-squared:  0.651,  Adjusted R-squared:  0.644 
## F-statistic: 89.6 on 1 and 48 DF,  p-value: 1.49e-12

summary(car)$adj.r.squared

## [1] 0.6438

summary(car)$r.squared

## [1] 0.6511

解除载入的包

detach(cars)