octave

问题 I want to create a pretty printed table from a matrix (or column vector). For Matlab there are several available functions that can do this (such as printmat, array2table , and table ), but for Octave I cannot find any. So instead of: >> a = rand(3,2)*10; >> round(a) ans = 2 10 1 3 2 1 I would like to see: >> a = rand(3,2)*10; >> pretty_print(round(a)) THIS THAT R1 2 10 R2 1 3 R3 2 1 How can I produce a pretty printed table from a matrix? (Any available package to do so?) UPDATE After trying

问题 I had a .csv file that I wanted to read into Octave (originally tried to use csvread). It was taking too long, so I tried to use R to workaround: How to read large matrix from a csv efficiently in Octave This is what I did in R: forest_test=read.csv('forest_test.csv') library(R.matlab) writeMat("forest_test.mat", forest_test_data=forest_test) and then I went back to Octave and did this: forest_test = load('forest_test.mat') This is not giving me a matrix, but a struct. What am I doing wrong?

问题 I'd like to try the SciPy suite instead of Octave for doing the statistics in my lab experiments. Most of my questions were answered here, there is just another thing left: I usually have an error attached to the measurements, in Octave I just did the following: R.val = 10; R.err = 0.1; U.val = 4; U.err = 0.1; And then I would calculate I with it like so: I.val = U.val / R.val; I.err = sqrt( (1 / R.val * U.err)^2 + (U.val / R.val^2 * R.err)^2 ); When I had a bunch of measurements, I usually

问题 I have some troubles in understanding how to implement events in octave/matlab, in the resolution of differential equations. Consider for example this simple code to solve the differential equation y' = -y: function dy = odefun(t,y) dy = -y; endfunction options = odeset('RelTol',1e-4,'AbsTol',[1e-4]); [T,Y] = ode45(@odefun,[0 12],[1],options); Now I would like to introduce a random event. For example at some fixed time step I would like to randomly change the value of y and then continue the

问题 I would like to : step 1) Rotate an image with 20 degrees using this code rotatedImage = imrotate(originalImage, 20); . step 2) calculate degree rotation used in step 1 based only on the rotated image if it possible or based on rotated image and the original image. there is any function in matlab could do the step 2 or a proposition to do that? 回答1: This example shows one way to perform step 2: A = 'peppers.jpg'; img = im2double(imread(A)); img_r=imrotate(img,20,'nearest','crop'); % <-- this

问题 I am getting familiarized with Octave and the function fft2() . In this toy example, I am aiming at producing the 2D DFT of the following 256 x 256 png image: To be able to understand the output easily, I try to convert this image into a 256 x 256 image, eliminating color information: Im = imread('circ.png'); pkg load image Im = rgb2gray(Im); figure, imshow(Im) After this bookkeeping preliminaries I run: A = fft2(double(Im)); OK. Now I take the same image, and analyze it with ImageJ, checking

问题 In Sublime, I'm trying to take the transpose of a row vector in an Octave file as such: y = [4, 5, 6]; y_transpose = y'; But whenever I try to run this in Octave, it acts as if introduction of the transpose operator (the ') is the beginning of a string, and ignores the following lines of code. How can I remedy this? 回答1: I don't know why it isn't working. ' is actually listed as an operator in the docs. But as a workaround, you could use the transpose function. y = [4, 5, 6]; y_transpose =

问题 Sorry about the poor title ;) I'm trying to recreate a matlab plot I've come across in some other work, but I don't quite understand the scale they are using. The y axis increments are as follows (from the top [+ve y]): 0.9999, 0.999, 0.99, 0.9, 0 I can use semilogy to plot a logarithmic graph, but this is kind of the wrong way round; my increments go 1, 0.1, 0.01, 0.001, etc which is actually 1 - i , where i is the increments I actually want! I don't entirely understand how to describe this

问题 Maybe I'm spoiled by Python, but does Octave allows one to assign the values of variables directly from a vector? That is, doing something like a,b,c=[5,6,7] will result with a=5, b=6, c=7 . I have tried many combinations of writing the expression above, but no luck yet ... 回答1: This can be done by constructing a cell array with "{...}" and converting this to a comma separated list via "{:}": [a b c] = {5 6 7}{:} a = 5 b = 6 c = 7 来源： https://stackoverflow.com/questions/9908398/octave-basics

问题 When writing a script that loads data, it's a waste of time to wait for it to load each time. How to check to see if the variable is defined? 回答1: You can use the exist function in Octave to do the work. It can be used to check the existence of given name as a variable, built in function, file, or directory. In you case, to check the existence of a variable, you may use something like this: if (exist("your_var_name", "var") == 1) printf("varname exists"); else printf("varname not exists");