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User:Sam Spade

Wikics templateEdit

Hi Petr! I've just created a new template to indicate English Wikipedia users who also contribute to the Czech Wikipedia.

Template:User wikics

Feel free to add it to your userboxes if you like it. Happy Easter. Daniel Šebesta (talkcontribs) 08:17, 14 April 2006 (UTC)

hi Petr, could you help us a little?Edit

you created the images:


could you, from the same source, create a PNG just like Image:Sampled.signal.png except that it is Sampled and Held, just as if the dirac sampled signal was passed through a properly scaled Zero-order hold ? it would look alot like Image:Digital.signal.png except the horizontal levels are not quantized. the held level is the same height as the resulting sample impulse. i am using Image:Sampled.signal.png and we could use this File:Sample and hold.signal.png or File:ZOH.signal.png (whatever you want to call it) image side-by-side with your Image:Sampled.signal.png to illustrate the effect of ZOH and conventional Digital to analog converter.

thanks in advance if you do this. r b-j 01:05, 3 June 2006 (UTC)

OK, I will try to do it soon. --Petr.adamek 15:13, 5 June 2006 (UTC)
Done, is it OK? --Petr.adamek 15:30, 5 June 2006 (UTC)
excellent! thank you, thank you, thank you, thank you, thank you, thank you, thank you, thank you, thank you, thank you. r b-j 21:07, 5 June 2006 (UTC)

sorry to bother you again, Petr. i use a Mac and i do not have gnuplot or whatever it is that you create these images with. i used your drawings in the Zero-order hold article. i'm feeling pressured to do another article for First-order hold (to replace an article that is not very good) could you do another one, just like Sampled.held.signal.png but with the left corners of the red graph connected with straight lines (replacing the piecewise constant with a piecewise linear function)? in other words, a linear interpolation of the identical sampled signal? i won't bug you for more drawings (i'll try to get someone else to do the ZOH and FOH impulse responses in the same format as your drawings). it's just that, even if i could draw similar graphs, you have the original signal definition (the gray curve in the back).

again, thanks in advance if you do this. r b-j 22:01, 11 June 2006 (UTC)

Petr, i just thought of something. if you do create this linear interpolated drawing that i would use for First-order hold, could you offset the red graph (the piecewise linear function) to the right by one sample period (representing a delay of one sample)? this way, the impulse response of the first-order hold would be causal and realizable and, as a bonus, the gray curve in the background would be more visible since the linear interpolation would obscure nearly all of it. again, i will not ask you to do another favor like this. i promise. again thanks. r b-j 22:30, 11 June 2006 (UTC)
Is this and this what do you want? If so, please suggest suitable image names and I will upload them to commons (or you can do it instead of me, I release it as Public Domain). If you need another images, I shall be pleased to create them. Images are created with dia and sources are available here. --Petr.adamek 23:03, 11 June 2006 (UTC)
i can make use of both of those images. one is a regular 1st-order hold response (that has an impulse response that is acausal) and the other is the same thing with a causal impulse response. thank you!!
if you are "pleased to create" 3 new images, using the same image size (but with the y-axis moved right to the center) and the same spacing tick marks on the x-axis, could you create a simple impulse response for the 0th-order hold (0 everywhere but some nice positive value 1/T for 0 < t < T), the standard acausal 1st-order hold (0 everywhere but linearly ramping up to 1/T for -T< t < 0 and ramping back down to 0 for 0 < t < T) and then the causal 1st-order hold (just like the acausal but with the impulse response bumped over to the right by one T unit)? there would be no gray background signal with these impulse response plots abd perhaps the tick marks need not be the vertical dotted lines but just a little tick on the x-axis. if all plots are done on the same scale with the same formatting, that will look real "slick" (an American figure of speech) and i think will help quickly transmit the knowledge i want to do with these articles. Take a look at Zero-order hold and Digital-to-analog converter to see what i did with your other plots. thank you for your help. r b-j 02:01, 12 June 2006 (UTC)

Petr, how do you get Dia to work. i am running Windows XP and i cannot unpack the bz2 or tar files. i just do not get how they expect anyone to use these programs. it's really stupid. r b-j 02:30, 13 June 2006 (UTC)

i finally got a download of Dia to work and was able to download your source, so it looks like i can make drawings with it. thanks for your help Petr. r b-j 03:18, 13 June 2006 (UTC)

Petr, I want to thank you for creating those signal images with their sampled and quantized variants and for your help in showing me how you did it and referring me to the source. I took your work and ran with it, creating (using the same continous-time "gray" signal in the background) a few other similar images for other files. Your simple drawings and the variations on the theme can be used to quickly illustrate the sometimes subtle differences between sampling, quantizing, digitizing, reconstructing, etc. This works so well because we have the very same original signal in gray in the background so the difference in the image is due only to a difference in the content of concept and not confused with a difference in what the original signal was. I also made some impulse response images to correspond with the signal images.

Now I uploaded my variants into Wiki-commons (where your images are) and they told me right away that they prefer SVG. so i re-exported the Dia images to SVG including your original images and uploaded them. i put on my uploaded PNG and your PNG files the {{SupersededSVG|newfile.svg}} tag as had been suggested. I also changed ALL references in the English Wikipedia (including your original contribs) to the PNG images to the SVG counterparts. I plan to have my PNG images quickly deleted in commons. Would you also like your PNG images deleted since they are not referenced anymore and i put the superseded tag on? I did credit you upon upload.

If you do not like what I did to your image files or to the articles that referred to them, please feel free to revert my changes. I just thought I was doing this the way they like it.

Again, thank you for your help in getting me up to speed on this Dia stuff and for providing the original images to base all of these sampling related concepts on. Best regards, r b-j 05:02, 17 June 2006 (UTC)

Thank you for converting images to svg format, original png versions can be deleted, of course. I wanted to convert them too, but unfortunatly I had no time to do it. BTW, I am very pleased that my images are useful :-). --Petr.adamek 19:11, 28 June 2006 (UTC)

i'm glad they existed and we were able to take the source and make additional images to illustrate a point. did you see what i did at digital-to-analog converter, zero-order hold, first-order hold, and Nyquist-Shannon sampling theorem? i put this to use. again thanks. (now i'm trying to figure out gnuplot so i can make some frequency response graphs. do you know how to do that?)r b-j 16:37, 29 June 2006 (UTC)


If you believe the person who impersonated you is the same person who previously impersonated -jkb-, you may file a CheckUser request to check whether your suspicions are correct or not. 01:17, 26 August 2006 (UTC)