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# Interpolation without FPoint arithmetics

 P: n/a Hi, Can somebody give me some hints how to do a line interpolation without using floating point arithemtics? The function shall do a linear interpolation between 2 points (line interp?) and it shall return the y value to any x value given. e.g. p1: (0,0) p2 (1000,50) y value to calculate at x=600 Is there a way to implement this not using any FP arithmetics in C? Perhaps "scaling up" or sth like this? Any help would be great Thanks in advance J. Ernst Nov 14 '05 #1
3 Replies

 P: n/a Jonas Ernst wrote: The function shall do a linear interpolation between 2 points (line interp?) and it shall return the y value to any x value given. e.g. p1: (0,0) p2 (1000,50) y value to calculate at x=600 y = 20*x ? How is this related to the C language? Nov 14 '05 #2

 P: n/a Jonas Ernst wrote: Hi, Can somebody give me some hints how to do a line interpolation without using floating point arithemtics? Yes. The function shall do a linear interpolation between 2 points (line interp?) and it shall return the y value to any x value given. e.g. p1: (0,0) p2 (1000,50) y value to calculate at x=600 Is there a way to implement this not using any FP arithmetics in C? Perhaps "scaling up" or sth like this? Yes. Most early graphics-oriented devices had no FP. The BetaCom devices I programmed (sold to Gould. What they did with BetaCom I don't know.) were 4K and 8K 12-bit PDP-8's with no FP. They did quite well. What we could do in PDP-8 assembler, you can do in C. Elementary graphics texts would be a help to you. Nov 14 '05 #3

 P: n/a Jonas Ernst wrote: Hi, Can somebody give me some hints how to do a line interpolation without using floating point arithemtics? The function shall do a linear interpolation between 2 points (line interp?) and it shall return the y value to any x value given. e.g. p1: (0,0) p2 (1000,50) y value to calculate at x=600 Is there a way to implement this not using any FP arithmetics in C? Perhaps "scaling up" or sth like this? Any help would be great Thanks in advance J. Ernst 1. Don't post separately to multiple newsgroups. If you are going to crosspost, append them to the "Newsgroup:" section of your post. For example, there are different replies to your post in news:comp.lang.c++ than this one. CC: news:comp.lang.c++ (for thread consistency) Followup-To: news:comp.programming 2. Your issue is about an algorithm or the process of getting something done (such as interpolation). The newsgroup news:comp.programming is an excellent place for algorithmic questions. Most all algorithms are language independent. 3. This also happens to be a mathematics issue, again independent of the programming language. Also try a newsgroup with the term "sci.math" in its name. 4. How do you want the interpolation performed? Linear Interpolation? Binomial Interpolation? Other? 5. Your issue may also fall under the relm of "curve fitting", which is the subject of determining the best equation to describe a set of points. If you have the equation then determining any other point is easy. However, determining the equation is not always easy. -- Thomas Matthews C++ newsgroup welcome message: http://www.slack.net/~shiva/welcome.txt C++ Faq: http://www.parashift.com/c++-faq-lite C Faq: http://www.eskimo.com/~scs/c-faq/top.html alt.comp.lang.learn.c-c++ faq: http://www.raos.demon.uk/acllc-c++/faq.html Other sites: http://www.josuttis.com -- C++ STL Library book Nov 14 '05 #4

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