inverse

I'm trying to convert an image into an audio signal in MATLAB by treating it as a spectrogram as in Aphex Twin's song on Windowlicker . Unfortunately, I'm having trouble getting a result. Here it what I have at the moment: function signal = imagetosignal(path, format) % Read in the image and make it symmetric. image = imread(path, format); image = [image; flipud(image)]; [row, column] = size(image); signal = []; % Take the ifft of each column of pixels and piece together the real-valued results. for i = 1 : column spectrogramWindow = image(:, i); R = abs(ifft(spectrogramWindow)); % Take only

Is it possible to calculate the inverse error function in C? I can find erf(x) in <math.h> which calculates the error function, but I can't find anything to do the inverse. Quick & dirty, tolerance under +-6e-3. Work based on "A handy approximation for the error function and its inverse" by Sergei Winitzki. C/C++ CODE: float myErfInv2(float x){ float tt1, tt2, lnx, sgn; sgn = (x < 0) ? -1.0f : 1.0f; x = (1 - x)*(1 + x); // x = 1 - x*x; lnx = logf(x); tt1 = 2/(PI*0.147) + 0.5f * lnx; tt2 = 1/(0.147) * lnx; return(sgn*sqrtf(-tt1 + sqrtf(tt1*tt1 - tt2))); } MATLAB sanity check: clear all, close

Hi i'm trying to figure out how to calculate the inverse of a quaternion. A code example would be awesome. Cheers Mihai Maruseac See Wikipedia article for the entire Quaternion math. Don't know what language you want to use but I'll try to give some hints in Haskell. data Quaternion = Q Double Double Double Double deriving (Show, Eq) First, you need to implement multiplication and addition of quaternions. instance Num Quaternion where (+) = q_plus (*) = q_mult --.... q_plus (Q a b c d) (Q a' b' c' d') = Q (a + a') (b + b') (c + c') (d + d') q_mult (Q a b c d) (Q a' b' c' d') = Q a'' b'' c'' d'

This question already has an answer here: Cleanest way to toggle a boolean variable in Java? 7 answers If you have a boolean variable: boolean myBool = true; I could get the inverse of this with an if/else clause: if (myBool == true) myBool = false; else myBool = true; Is there a more concise way to do this? Just assign using the logical NOT operator ! like you tend to do in your condition statements ( if , for , while ...). You're working with a boolean value already, so it'll flip true to false (and vice versa): myBool = !myBool; An even cooler way (that is more concise than myBool = !myBool

This is really a variation on this question, but not a duplicate: Python reverse / invert a mapping Given a dictionary like so: mydict= { 'a': ['b', 'c'], 'd': ['e', 'f'] } How can one invert this dict to get: inv_mydict = { 'b':'a', 'c':'a', 'e':'d', 'f':'d' } Note that values span uniquely under each key. Note : I previously had syntax map = ... and dict = ... Reminder not to use map and dict as they are built-in functions, see excellent comments and answers below :) TL;DR Use dictionary comprehension, like this >>> my_map = { 'a': ['b', 'c'], 'd': ['e', 'f'] } >>> {value: key for key in my

My Problem: I want to count inverse in the for loop. This is the opposite of what I want to do: for($i=1;$i<=10;$i++){ echo $i; } If I put $i-- doesn't works (my server crashes). Help meeee! Best Regards, Adam When you say $i-- crashes your server, did you change the initialization and condition for $i ? for($i=10; $i>=1; $i--){ echo $i; } If you take the for as you wrote and just replace $i++ with $i-- , the value of $i will be decremented with every iteration (1, 0, -1, -2, etc.) and the looping condition $i<=10 is always true. If you want to count backwards, you also need to change the