R中2個觀測值的線性回歸

Question

我正在嘗試基於兩個觀察結果進行簡單的回歸：

> x=c(1,2)
> y=c(3,5)
> fit <- lm(y ~ x)
> Prediction <- predict(fit, newdata=c(3,4))
Error in eval(predvars, data, env) : 
  numeric 'envir' arg not of length one
> summary(fit)

Call:
lm(formula = y ~ x)

Residuals:
ALL 2 residuals are 0: no residual degrees of freedom!

Coefficients:
            Estimate Std. Error t value Pr(>|t|)
(Intercept)        1         NA      NA       NA
x                  2         NA      NA       NA

Residual standard error: NaN on 0 degrees of freedom
Multiple R-squared:      1, Adjusted R-squared:    NaN 
F-statistic:   NaN on 1 and 0 DF,  p-value: NA

我知道我不應該在模型中得到任何殘差，但是為什么我不能預測x的未來值？

Answer 1

我認為newdata必須采用list()形式。

predict(fit, newdata=list(x=c(3,4)))