R程序下载包caret 打开时不可以问题出在哪？

Warning in install.packages :

  downloaded length 110592 != reported length 4121711

package ‘colorspace’ successfully unpacked and MD5 sums checked

package ‘RColorBrewer’ successfully unpacked and MD5 sums checked

package ‘dichromat’ successfully unpacked and MD5 sums checked

package ‘munsell’ successfully unpacked and MD5 sums checked

package ‘labeling’ successfully unpacked and MD5 sums checked

Warning in install.packages :

  error 1 in extracting from zip file

Warning in install.packages :

  cannot open compressed file 'SparseM/DESCRIPTION', probable reason 'No such file or directory'

Error in install.packages : cannot open the connection

> library(caret)

Error in library(caret) : 不存在叫‘caret’这个名字的程辑包

> library("caret")

Error in library("caret") : 不存在叫‘caret’这个名字的程辑包

> 

为什么会这样？