if you know the number of columns before hand: >>> xs = np.array([[1,2,3,4,5],[10,20,30,40,50]]) >>> ys = np.array([], dtype=np.int64).reshape(0,5) >>> ys array([], shape=(0, 5), dtype=int64) >>> np.vstack([ys, xs]) array([[ 1., 2., 3., 4., 5.], [ 10., 20., 30., 40., 50.]]) if not: >>> ys = np.array([]) >>> ys = np.vstack([ys, xs]) if ys.size else xs array([[ … Read more
in numpy you have where : >> import numpy as np >> x = np.random.randint(0, 20, 10) >> x array([14, 13, 1, 15, 8, 0, 17, 11, 19, 13]) >> np.where(x > 10) (array([0, 1, 3, 6, 7, 8, 9], dtype=int64),)
There are a few ways to do this. One way to do this is to get all the children of the root object (represented in prior versions by the handle 0): figHandles = get(groot, ‘Children’); % Since version R2014b figHandles = get(0, ‘Children’); % Earlier versions Or you could use the function findobj: figHandles = … Read more
The problem you’re having relates to how floating-point numbers are represented on a computer. A more detailed discussion of floating-point representations appears towards the end of my answer (The “Floating-point representation” section). The TL;DR version: because computers have finite amounts of memory, numbers can only be represented with finite precision. Thus, the accuracy of floating-point … Read more
Many ways to do this. ismember is the first that comes to mind, since it is a set membership action you wish to take. Thus X = primes(20); ismember([15 17],X) ans = 0 1 Since 15 is not prime, but 17 is, ismember has done its job well here. Of course, find (or any) will … Read more
I prefer using structures for my options. This gives you an easy way to store the options and an easy way to define them. Also, the whole thing becomes rather compact. function example(varargin) %# define defaults at the beginning of the code so that you do not need to %# scroll way down in case … Read more
They’re doubles. vpa() is simply choosing to display non-significant digits beyond the floating point relative accuracy, where printf() and disp() truncate or zero them out. You’re only getting your original four digits back out because the literal you chose to initialize num with just happens to be the exact decimal expansion of a binary double … Read more
There are a few different options on how to do this. The most basic is to use varargin, and then use nargin, size etc. to determine whether the optional arguments have been passed to the function. % Function that takes two arguments, X & Y, followed by a variable % number of additional arguments function … Read more
Using the built-in profiler to see where the hot parts of my code are: profile on % some lines of code profile off profile viewer or just using the built in tic and toc to get quick timings: tic; % some lines of code toc;
Have a look at Determine and count unique values of an array. Or, to count the number of occurrences of 5, simply do sum(your_matrix == 5)