Javascript, visualization and statistics (Protovis and Jstat)

Last week I got faced with two very interesting libraries.

Protovis
Protovis uses JavaScript and SVG for web-native visualizations. Protovis composes custom views of data with simple marks such as bars and dots.

Unlike low-level graphics libraries that quickly become tedious for visualization, Protovis defines marks through dynamic properties that encode data, allowing inheritance, scales and layouts to simplify construction.

jStat

jStat is a statistical library written in JavaScript that allows you to perform advanced statistical operations without the need of a dedicated statistical language (i.e. MATLAB or R).

Read Write Web has also an article about other 20 JavaScript Libraries for Data Visualization

Comments

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> void uSleep ( 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); } T

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!

powerpoint slides to jpeg

Looking for some way to convert power point slides to JPG, I've found this site: http://www.commandlinefu.com/commands/browse It has tons of good linux command line tips. And here is the tip about the pdf to jpg which brought me there: http://www.commandlinefu.com/commands/view/719/convert-pdf-to-jpg And to convert the powerpoint to pdf before, one can issue the unoconv command: unoconv -f pdf slides.ppt

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