R Error: package 'mvtnorm' required by 

问题:

I need to install the package multcomp. After installing the package (install.packages("multcomp")) I get the message:

package ‘zoo’ successfully unpacked and MD5 sums checked
package ‘mvtnorm’ successfully unpacked and MD5 sums checked
package ‘TH.data’ successfully unpacked and MD5 sums checked
package ‘sandwich’ successfully unpacked and MD5 sums checked
package ‘multcomp’ successfully unpacked and MD5 sums checked

The downloaded binary packages are in
    C:\Users\kbn982\AppData\Local\Temp\RtmpwbLdqW\downloaded_packages 

But when I load the library an error message appears:

Error: package 'mvtnorm' required by 'multcomp' could not be found .

I also tried to change the library location installing it into another path. But I don't have a clue why I get this message.