using 'R' in sage: can not plot. errors of X11 and PNG
Hi! We are going to use SAGE this semester in a course which has a piece of statistics. For this part we planned to compile Sage worksheets with the option 'R'. But we have the following errors. If we write the instruction:
the instruction works in a mac which has a local sage (packages are on the hard disk). However, the pupils will use the sage server of our university (v4.6), wich gives the error message:
Error in png() : X11 is not available
The same error is obtained with a local installation on windows 7 (v4.7.2, with VM virtual box).
Besides, if we try at sage server on sagenb.org (v4.7.2), we obtain a different error:
Error in X11(paste("png::", filename, sep = ""), width, height, pointsize, : unable to start device PNG In addition: Warning message: In png() : no png support in this version of R
Please, does anybody know how to fix it?