Skip to main content

Warning against using pie charts

Bernhard Reiter had wrote a really nice warning against using pie charts, and he did put it on his plotting tool ;-)

Here is a peace:
"... Piecharts are generally not recommended to visualise information! Use bar- or pointchars instead if the quantities are important. Studies have shown that piecharts are hard to read if you actually have to answer questions about the numbers they represent. They look very pleasing and are used in a lot of places but they do not help to visualise information that well. Analytic thing person will read the percentages or values given on the legend or the chart itself and analyse them in their head. ... "
Check the full text at his web site.

Comments

Popular posts from this blog

uSleep on windows (win32)

I am facing a terrible issue regarding timing on windows.

Googling arround, I've found those infos:
Using QueryPerformanceCounter and QueryPerformanceFrequency APIs in Dev-C++
(http://yeohhs.blogspot.com/2005/08/using-queryperformancecounter-and_13.html)
QueryPerformanceCounter() vs. GetTickCount()
http://www.delphifaq.com/faq/delphi_windows_API/f345.shtml
How to time a block of code
http://www.cryer.co.uk/brian/delphi/howto_time_code.htm
And Results of some quick research on timing in Win32 http://www.geisswerks.com/ryan/FAQS/timing.html
With that I'm trying to write something like a uSleep function for windows:


#include<windows.h>

voiduSleep(int waitTime){
__int64 time1 = 0, time2 = 0, sysFreq = 0;

QueryPerformanceCounter((LARGE_INTEGER *)&time1);
QueryPerformanceFrequency((LARGE_INTEGER *)&freq);
do{
QueryPerformanceCounter((LARGE_INTEGER *)&time2);

// }while((((time2-time1)*1.0)/sysFreq)<waitTime);
}while( (time2-time1) <waitTime);
}

There is also already a nanosleep…

More trickery with gnuplot dumb terminal

In my post "Plotting memory usage on console" the chart doesn't pan the data.
Now, using a named pipe, the effect got a little bit nicer.
First, we have to run the memUsage.sh script to get a file filled with memory usage info:
./memUsage.sh > memUsage.dat &
Then we have to create a named pipe:
mkfifo pipe
Now we have to run another process to tail only the last 64 lines from the memUsage.dat
while [ 1 ]; do tail -64 memUsage.dat> pipe; done &
And now we just have to plot the data from the pipe:
watch -n 1 'gnuplot -e "set terminal dumb;p \"pipe\" with lines"'
And that is it!

Checking auth.log for ssh brute force attacks

As I am letting my personal computer always on, as a homelinux server, I decided to check if someone is trying to breaking in with SSH brute force attacks.

First I did a grep for fail at the /var/log/auth.log. (grep -i /var/log/auth.log)

And I got lots of lines with the string "fail". With [grep -i /var/log/auth.log | wc -l] I figured out that were 1164 fail entries at auth.log

With an [grep -i fail auth.log | cut -d " " -f 6 | sort | uniq] I checked that were two kind of failed attempts:
Failed
pam_unix(sshd:auth):

So I wrote the following line to check with which users they were attempting to log:
grep Failed auth.log | cut -d " " -f 11 | sort | uniq | while read line ; do echo -n $line" "; grep $line auth.log | wc -l; done | sort -n -k 2

Here, the field position (the number 11 at the above command lines [-f 11]) may change in some systems. At my desktop at work, the username came at the position 9.

Here are the "top ten":
root 2922
user 2884