Suppose that I have two numpy arrays of the form x = [[1,2] [2,4] [3,6] [4,NaN] [5,10]] y = [[0,-5] [1,0] [2,5] [5,20] [6,25]] is there an efficient way to merge them such that I have xmy = [[0, NaN, -5 ] [1, 2, 0 ] [2, 4, 5 ] [3, 6, NaN] [4, NaN, NaN] ...
I'd like to roll a 2D numpy in python, except that I'd like pad the ends with zeros rather than roll the data as if its periodic. Specifically, the following code import numpy as np x = np.array([[1, 2, 3],[4, 5, 6]]) np.roll(x,1,axis=1) returns array([[3, 1, 2],[6, 4, 5]]) but what I would prefer is array([[0, 1, 2], [0, 4, 5]...
I'm trying to export data to a csv file. It should contain a header (from datastack) and restacked arrays with my data (from datastack). One line in datastack has the same length as dataset. The code below works but it removes parts of the first line from datastack. Any ideas why that could be? s = ','.join(itertools.chain(dataset)) + ...
Hello Everybody, I want to get the index of the min value of a numpy array that contains NaNs and I want them ignored >>> a = array([ nan, 2.5, 3., nan, 4., 5.]) >>> a array([ NaN, 2.5, 3. , NaN, 4. , 5. ]) if I run argmin, it returns the index of the first NaN >>> a.argmin() 0 I substitute NaNs with Infs a...
How can I sort an array in numpy by the nth column? e.g. a = array([[1,2,3],[4,5,6],[0,0,1]]) I'd like to sort by the second column, such that I get back: array([[0,0,1],[1,2,3],[4,5,6]]) thanks. ...
I have a set of trajectories, made up of points along the trajectory, and with the coordinates associated with each point. I store these in a 3d array ( trajectory, point, param). I want to find the set of r trajectories that have the maximum accumulated distance between the possible pairwise combinations of these trajectories. My first ...
Hello Everybody, I need a function that returns non-NaN values from an array. Currently I am doing it this way: >>> a = np.array([np.nan, 1, 2]) >>> a array([ NaN, 1., 2.]) >>> np.invert(np.isnan(a)) array([False, True, True], dtype=bool) >>> a[np.invert(np.isnan(a))] array([ 1., 2.]) Python: 2.6.4 numpy: 1.3.0 Please share...
Alright, i had this homework recently (don't worry, i've already done it, but in c++) but I got curious how i could do it in python. The problem is about 2 light sources that emit light. I won't get into details tho. Here's the code (that I've managed to optimize a bit in the latter part): import math, array import numpy as np from PIL...
Hi, Can someone gives me an example of how to save a 2-d matrix in a file and reloading it for furthur use? thanks ...
How can a list of vectors be elegantly normalized, in NumPy? Here is an example that does not work: from numpy import * vectors = array([arange(10), arange(10)]) # All x's, then all y's norms = apply_along_axis(linalg.norm, 0, vectors) # Now, what I was expecting would work: print vectors.T / norms # vectors.T has 10 elements, as d...
I'd like to make a class extending the numpy array base type, class LemmaMatrix(numpy.ndarray): @classmethod def init_from_corpus(cls, ...): cls(numpy.empty(...)) But apparently, it will not allow multi-dimensional array types. Is there a way around this? Thanks in advance! ndarray(empty([3, 3])) TypeError: only length-1 arra...
I am having trouble reading a csv file, delimited by tabs, in python. I use the following function: def csv2array(filename, skiprows=0, delimiter='\t', raw_header=False, missing=None, with_header=True): """ Parse a file name into an array. Return the array and additional header lines. By default, parse the header lines into ...
given a list of python strings, how can I automatically convert them to their correct type? Meaning, if I have: ["hello", "3", "3.64", "-1"] I'd like this to be converted to the list ["hello", 3, 3.64, -1] where the first element is a stirng, the second an int, the third a float and the fourth an int. how can I do this? thanks....
I have a dictionary whose keys are strings and values are numpy arrays, e.g.: data = {'a': array([1,2,3]), 'b': array([4,5,6]), 'c': array([7,8,9])} I want to compute a statistic between all pairs of values in 'data' and build an n by x matrix that stores the result. Assume that I know the order of the keys, i.e. I have a list of "la...
In NumPy functions, there are often initial lines that do checking of variable types, forcing them to be certain types, etc. Can someone explain the point of these lines in scipy.signal.square? What does subtracting a value from itself do? t,w = asarray(t), asarray(duty) w = asarray(w + (t-t)) t = asarray(t + (w-w)) source ...
Python currently uses Numpy for heavy duty math and image processing. The earlier Numeric and Numarray are obsolete, but still today there are many tutorials, notes, sample code and other documentation using them. Some of these cover special topics of interest, some are well written but haven't been updated or replaced, or are otherw...
Hello, I'm curious, whether there is any way to print formated numpy.arrays, e.g., in the way similar to this: x = 1.23456 print '%.3f' % x If I want to print the numpy.array of floats, it prints several decimals, often in 'scientific' format, which is rather hard to read even for low-dimensional arrays. However, numpy.array apparent...
Greetings, I am trying to bin an array of points (x, y) into an array of boxes [(x0, y0), (x1, y0), (x0, y1), (x1, y1)] (tuples are the corner points) So far I have the following routine: def isInside(self, point, x0, x1, y0, y1): pr1 = getProduct(point, (x0, y0), (x1, y0)) if pr1 >= 0: pr2 = getProduct(point, (x1, y0)...
How can I run hierarchical clustering on a correlation matrix in scipy/numpy? I have a matrix of 100 rows by 9 columns, and I'd like to hierarchically clustering by correlations of each entry across the 9 conditions. I'd like to use 1-pearson correlation as the distances for clustering. Assuming I have a numpy array "X" that contains ...
Hi all I would like to append a value at the end of my numpy.array. I saw numpy.append function but this performs an exact copy of the original array adding at last my new value. I would like to avoid copies since my arrays are big. I am using resize method and then set the last index available to the new value. Can you confirm that r...