If you show us your data/code/output as has been requested, then we may be able to tell which it is. Without that information you are expecting either R or the members of the list to read your mind. I keep making notes to my future self to use the timetravel package (not written yet, that’s why I need my future self to use it) to send a copy of the esp package (also not written yet) back in time to me so I can use it for situations like this. But so far that has not worked (maybe my future self is even more lazy than my present self, or my near future self does something to offend my far future self enough that he is unwilling to do this small favor for my current past self, darn, either way means I should probably do better on the diet/exercise).

x <- rep(1:3,5)

You have to then type x to see it:

> x
 [1] 1 2 3 1 2 3 1 2 3 1 2 3 1 2 3

You can exploit this fact for doing a quick-and-dirty lottery. Assume you have a file with email addresses, one per line, called "entries.txt". First, read them and assign them to an object:

entries <- readLines("entries.txt")

Next, create an index of numbers of the same length but in random order:

index <- sample(1:length(entries),length(entries))

Note that you don't see it unless you type index. Combine index and emails in a dataframe (also not directly visible):

dat <- data.frame(cbind(index,entries))

Now, go to random.org and draw a number from the index. Type dat to reveal who you drew. This method makes it a bit more "blind" and a bit less likely that you'll cheat.

• Create a text file that contains all the recipients, one on each line. This can be the full e-mail address, or it can be the alias you have defined in your mutt aliases file (which is your mutt “addressbook”). For our example, we’ll call it recipients.txt
• Create a text file with the text of your message. Let’s call it message.txt.
• Create a bash shell script containing the following:

  #!/bin/bash
  while read line
  do
  mutt $line -s 'Message subject'  < message.txt
  done < recipients.txt

  Where "Message subject" is whatever your message subject should be. Of course, you need to run your shell script from the directory in which the files "message.txt" and "recipients.txt" are stored. Otherwise, you need to substitute their names with the full path name, e.g. ~/message.txt.

• Make your bash script executable and run it. Done. Your individual e-mails should show up in your mailfolder for sent mail (defined by set record=... in your ~/.muttrc.

(zenity:22981): Gtk-WARNING **: cannot open display:

Sure, I hadn’t specified a display. So I tried setting the DISPLAY explicitly in my ~/.crontab:

* * * * export DISPLAY=:0.0 && /path/to/checklog

but then I got:

No protocol specified

(zenity:24101): Gtk-WARNING **: cannot open display: :0

The same happened when I tried running other X apps, like audacious. A line in ~/.crontab like this:

* * * * * DISPLAY=:0 /usr/bin/audacious

resulted in errors like this:

No protocol specified
/usr/bin/audacious: Unable to open display, exiting.

It turns out I needed to set, in my ~/.bashrc:

xhost local:mpromber > /dev/null

to allow crontab access to my X display. It now works, either using “export DISPLAY=:0.0″ in the ~/.crontab, or alternatively just using

zenity --notification --display=:0.0

in the script that checks for queued mail.

In the latest versions of Ubuntu or Xubuntu, you can change the welcome message via the settings menu for “Login Window” (or, at a command line, type “gksudo gdmsetup”). Go to the “local” tab.

However, the custom welcome message is not displayed for a lot of (possibly most or all of) the themes, if you want a themed login window. My guess is that this is because these themes do not display a welcome message at all, period. To work around this, you can manually edit the .xml file of the theme you wish to use. Let’s assume you want to use the “Human” theme for your login screen. Pick that in the gdm setup window. Set your custom welcome message. Now, go to /usr/share/gdm/themes. You will see that this contains folders named after the different themes. You want to change the “Human” theme, so go to that folder. Now, using sudo, edit the file Human.xml. You will see that it contains xml markup, which is similar to hmtl. Add a section that looks like the following (I don’t think it matters where you add it. I added mine after the “ubuntu logo” section and it works fine):

  <!-- Welcome message (added by MP) -->
  <item type="label">
    <pos y="2%" x="2%"/>
    <normal color="#000000" font="Sans 14"/>
    <!-- Stock label for: Welcome to %h -->
    <stock type="welcome-label"/>
  </item>

Of course, you can change the position, color and font; this should be easy to figure out. Save the file. Next time you log out, you will see the custom welcome message that you have defined in the GUI for the gdm settings on your login screen.

?"&"

I still fall from it from time to time. (I think it has to do with my rudimentary knowledge and usage of “&&” for if-statements in bash shell scripts.

Below I just go through “&&” and “&”. Obviously, this also applies to “||” and “|”.

Here’s a little demo to remind me and to demonstrate this to newbies:

> 1==1
[1] TRUE
> 1==1 & 1==2
[1] FALSE
> 1==1 && 1==2
[1] FALSE

So far, so good. Now look what happens if we apply this to vectors:

> 1:3==1:3
[1] TRUE TRUE TRUE
> 1:3==c(1,3,3)
[1]  TRUE FALSE  TRUE
> 1:3==1:3 & 1:3==c(1,3,3)
[1]  TRUE FALSE  TRUE

This is what you probably want in most cases: element-wise comparison. The “&” here compares each element in the vector “TRUE TRUE TRUE” to the corresponding element in “TRUE FALSE TRUE” and returns a “TRUE” each time they match and a “FALSE” if they don’t. Now look what happens if we use “&&”:

> 1:3==1:3 && 1:3==1:3
[1] TRUE
> 1:3==1:3 && 1:3==c(1,3,3)
[1] TRUE

For “&&”, as the R help page says, “The longer form evaluates left to right examining only the first element of each vector.”

This is quite obvious in this example, but it can get confusing when you use a logical operator to index a vector. Watch this:

> x <- 1:5
> x[x<5]
[1] 1 2 3 4
> x[x<5 & x>2]
[1] 3 4

Fine.

> x[x<5 && x>2]
integer(0)

The reason:

> x>2 & x<5
[1] FALSE FALSE  TRUE  TRUE FALSE
> x>2 && x<5
[1] FALSE

So in the first case, R "sees"

> x[c(FALSE,FALSE,TRUE,TRUE,FALSE)]

and in the second case, it sees:

> x[FALSE]

As long as the first element compares with "FALSE", you're actually lucky, because the error will be obvious. It's tricky when "&&" evaluates to "TRUE" when it looks at the first element, because some R functions will recycle input if it is too short, and this can lead to things like:

> x <- 1:10
> y <- c(1,3:11)
> x==y
 [1]  TRUE FALSE FALSE FALSE FALSE FALSE FALSE FALSE FALSE FALSE
> x[x==1 & y==1]
[1] 1
> x[x==1 && y==1]
 [1]  1  2  3  4  5  6  7  8  9 10

So basically, for logical comparison, stick to "&" unless you know you need "&&".

By the way, if you want to see the values that are elements of both x an y, use "%in%":

> x[x%in%y]
[1]  1  3  4  5  6  7  8  9 10
> y[y%in%x]
[1]  1  3  4  5  6  7  8  9 10

But don't do:

> y[x%in%y]
[1]  1  4  5  6  7  8  9 10 11

This indexes y using the logical vector returned by "x%in%y", which is of course:

> x%in%y
 [1]  TRUE FALSE  TRUE  TRUE  TRUE  TRUE  TRUE  TRUE  TRUE  TRUE

sudo aptitude install imagemagick

ImageMagick is worth getting for a lot of other reasons, too, just see man convert or man mogrify after installing.

Here are the most important options for import

import pic.jpg

This changes the cursor to a crosshair — draw around the region you want a screenshot of; no need to take a screenshot of the entire screen and then crop. Combined with a verve mini commandline in the Xfce panel, this is ideal for taking quick images of order confirmations, error messages that you need to google later, etc.

import -screen pic.jpg

This also changes the cursor to a crosshair, but instead of drawing a region, you point it at one of your windows and click, and you get a screenshot of that window only.

import -window root pic.jpg
import -pause 2 -window root pic.jpg

Screenshot of the entire screen, without or with a delay.

My only gripe with import is that it doesn’t do transparency, at least not by default (for example, transparent terminals are opaque black in the screenshot), and probably related is that it loses some of my window borders (I’m using Compiz & Emerald). With the gazillion options, I’m sure there’s some way to fix it, but I have no time to figure it out. For pretty screenshots of transparent windows, I did instead:

sudo aptitude install gnome-utils

and use gnome-screenshot (which instead has the advantage that you don’t necessarily have to save the screenshot — you can drag and drop the thumbnail preview from the save dialogues to apps that are capable of receiving drag and drop).

This will give you a graphical interface and guide you through each step to get the basic setup.

mpromber@audrey:/dev$ ls -l video0
crw-rw---- 1 root video 81, 0 2008-04-14 16:48 video0

Turns out I didn’t have a group video so I had to create it and add my user (via Xfce Menu → System → Users and Groups). Log out and back in; works.

Note that this syncs several machines via the remote server. If you don’t have access to a remote server, set up ~/tomboy-sync on one of your local machines. Then sync the other machines to that via SSH just as in the setup above, and sync Tomboy on the machine that hosts ~/tomboy-sync to that folder via Tomboy’s “sync to local folder” option.

Also note that I can just say “isomerica” here instead of the full server name because I have an entry for that host in ~/.ssh/config that looks something like this:

Host isomerica
Hostname colobus.isomerica.net