title: R plot: Insert text in the middle of device region when showing multiple plots
body: <p>I have a plot with a 4x3 format, however only 10 plots are shown.</p>
  
  <pre><code>par(mfrow=c(4,3)) #Grid layout
  </code></pre>
  
  <p>Now I want to insert one legend for all! plots in the middle of the complete device region and at the far right corner another text for some info. However right now with this code, the legend is in the middle of the last(!) small plot and the text at the far right corner of the last plot. How can I move them both into the middle of my device?</p>
  
  <pre><code>  #Legend
    par(xpd=NA)
    legend(legend="Legend", col=hblue,lty=1, lwd=2, bty="n", text.col="black", ncol=1, "bottom", 
           inset = c(0.0, -.1),cex=0.65) 
  
    #Inserting the source of data
    text_note=paste("Source:")
    mtext(text_note ,cex=0.4,col=hgrey,side = 1, line = 4, outer = FALSE,padj=0,adj=1)
  </code></pre>