[R] bootstrapping - number of items to replace is not a multiple of replacement length

[Gabriela Bucini]

Hello,

I'm new to boostrapping and I'd need some help to understand the error
message that pops up when I run my script.

I have a data.frame with 73 lines and 21 column.
I am running a stepwise regression to find the best model using the R
function "step".
I apply bootstrapping to obtain model coefficients.
This is my script:

# "datare80" is the name of the data.frame and "woodycover" is the response
variable
theta <- function(datare80, indices) {
             d <- datare80[indices, ]    # allows boot to select subsample
datasets
             full <- lm(d$woodycover~ ., data= d )
             lmbroadst <- step(full, data=d , direction = "both", k=2,
trace=0)
             coefficients(lmbroadst)  # return coef. vector
          }
resb <- boot(data = datare80, statistic = theta, R=1000)



When I run it, I get these two messages:
If I omit the last line "coefficients(lmbroadst)" in the function
definition, I get :
"Error in t.star[r, ] <- statistic(data, i[r, ], ...) :
        incorrect number of subscripts on matrix"
If I have the last line "coefficients(lmbroadst)", then I get:
"Error in t.star[r, ] <- statistic(data, i[r, ], ...) :
        number of items to replace is not a multiple of replacement length"


Thank you very much for any help!

Gabriela