如何在R中使用数据框进行方差分析

Question

I am currently learning R and am playing around with a dataset that has four nominal variables (Hour.Of.Arrival, Mode, Unit, Weekday), and a continuous dependent variable (Overall). This is all imported from a .csv in a data frame named basic. What I am trying to do is run an ANOVA just using this data frame, without creating separate vectors (eg Mode<-basic$Mode). "Fit" holds the results of the ANOVA. Here is the code that I wrote:

Fit<-aov(basic["Overall"],basic["Unit"],data=basic)

However, I keep getting the error

"Error in terms.default(formula, "Error", data = data) : no terms component nor attribute

I hope this question isn't too basic!!

Thanks :)

Answer 1

I think you want something more like Fit<-aov(Overall ~ Unit,data=basic) . The Overall ~ Unit tells R to treat Overall as an outcome being predicted by Unit ; you already specify that the dataframe to find these variables is basic.

Here's an example to show you how it works:

> y <- rnorm(100)
> x <- factor(rep(c('A', 'B', 'C', 'D'), each = 25))
> dat <- data.frame(x, y)
> aov(y ~ x, data = dat)
Call:
   aov(formula = y ~ x, data = dat)

Terms:
                        x Residuals
Sum of Squares    2.72218 114.54631
Deg. of Freedom         3        96

Residual standard error: 1.092333
Estimated effects may be unbalanced

Note, you don't need to use the data argument, you could also use aov(dat$y ~ dat$x) , but the first argument to the function should be a formula.