Vectorization refers to a programming paradigm where functions operate on whole arrays in one go. This affords benefits in terms of function calls, memory access, parallelization and code expressiveness. Some programming languages, such as MATLAB, are optimised to give the best performance when ...
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1answer
23 views
Updating an inventory with R using apply functions
I have created an inventory that works via QR codes. Briefly: the QR code codes for an email with the book/student checking it out. The email is downloaded into R using the gmailR package (code not ...
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vote
1answer
54 views
5
votes
2answers
154 views
Efficient element-wise function computation in Python
I have the following optimization problem:
Given two np.arrays X,Y and a function K I ...
4
votes
1answer
117 views
Optimization of multiple arrays for filtering
My app will be running on an iPad with A7. I pass in 3 JSON arrays and right now do some simple filtering, in the future the operation will be much more complicated. I realize the ...
1
vote
2answers
45 views
Scaling and incrementing non-zero elements of a NumPy matrix
I have a NumPy matrix C and want create a copy of it cPrime, which has some operation of the original matrix to all non-zero ...
3
votes
1answer
75 views
Vectorized numpy version of arange with multiple start stop
Given a single start and stop, numpy.arange is a good solution for building a NumPy array of evenly spaced values. However, given an array of start and an array of ...
1
vote
1answer
40 views
NumPy eliminate double loop
How can I vectorize this code snippet and eliminate this double loop? Even with "only" 1001 elements in a this takes almost 30s.
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1
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1answer
87 views
Optimize matlab triple for loop
I have a large matrix samples, I want to make another matrix sampleProb which is the same size, but modified as below:
...
2
votes
1answer
44 views
Modeling and plotting neuron responses
I want to assign the row of a matrix the return value of a function, but the only way I can figure out how to do this is with a for-loop. I'm assuming this is bad ...
1
vote
2answers
374 views
Generate random unit vectors around circle
I'm trying to generate a bunch of uniformly distributed unit vectors around the unit circle. Here's my code, which is working, but unfortunately I have a for-loop. How do I get rid of this for-loop?
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4
votes
1answer
71 views
Vectorization for temperature simulation
I'm new to Matlab and I would like to know tips in order to reduce the processing time of such program. The scheme of the actual code is very similar to typical C++ code and I would like to vectorize ...
2
votes
0answers
71 views
Speeding up loop-rich Matlab function to calculate temperature distribution
I would like to speed up this function as much as possible in Matlab.
This is part of a bigger simulation project, and as it is one of the most called functions within the simulation, this is crucial.
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3
votes
2answers
87 views
Improving Matlab function within big simulation
I have a very big Matlab simulation project in my hands, which I wanted to optimize, since I'm running it many times to tune parameters and the like.
Using Matlab's ...
3
votes
1answer
52 views
Fast counting of interactions between groups given users interactions and groups assignments
Given:
An array c that contains the group assignment of every user (c[i]=4 indicates that user i belongs to group 4)
A matrix ...
5
votes
1answer
106 views
Vector comparison inside for-loop
The following code finds no-rain periods in a time series that were preceded by rain over a threshold (e.g. 10mm in 2 days [k=48]).
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2
votes
2answers
439 views
Extracting maximum values from each of the subsets of an array
Problem description:
I have a numpy array cps from which I want to extract the maximum value in each of the
subsets of the array (a subset is defined as non-zero ...
4
votes
1answer
113 views
Bernoulli trials using a condition in a vectorized operation
I was wondering how to vectorize the following code instead of using the for-loop and still be able to check for a condition.
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5
votes
1answer
88 views
Optimizing a loop for catalogue manipulation
I have a catalogue of 56000 objects and I want to replace some columns with new values for instance replace NaN with -99 and ...
3
votes
2answers
68 views
Determining the value of a position on an array based on its nearest datapoint known value
I was wondering what would be the efficient way to determine the value of a position on an array based on its nearest datapoint known value in Python?
Problem description:
There are ...
3
votes
1answer
1k views
Run length encoding of vectors in MATLAB: looped version and vectorized version
A project I'm working on requires something akin to run length encoding on a vector in matlab. The data is in the form of a numeric vector, and the output is in the form of two vectors, ...
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vote
0answers
183 views
Efficient C Code Alternative to MATLAB's im2col
The function im2col in MATLAB is very useful to vectorize Patch based Image Processing algorithms.
The problem is the function isn't optimized and doesn't use C ...
3
votes
2answers
96 views
Calculating mesh centers runs very slowly
I have a piece of code that is used to calculate the cell centers in a rectangular mesh. The mesh size is pretty large (650 columns by 1150 rows). The code runs very slowly. I was wondering if I could ...
6
votes
1answer
207 views
Merging overlapping/intersecting string vectors
I am trying to merge overlapping/intersecting sets given as a list of string vectors below in R (my actual data set has thousands of such sets). The overlap/intersection is based on the ...
4
votes
1answer
166 views
Vectorize Matlab sum
I have the following Matlab function:
function [res] = a3_funct(x)
res = 0;
for i = 1:size(x,1)
res = res + abs(x(i))^(i+1);
end
end
It's ...
3
votes
1answer
318 views
Using Gibbs sampling to segment an image
I have been reading some NumPy guides but can't seem to figure it out. My TA told me I should be able to speed up my code by using a NumPy array instead of a for ...
