## Matrix implementation

I am trying to implement an optimal and fast running matrix in C++. I need some review of the code and ideas on how to improve the code quality if it shall be. class Matrix { // Some static assertions and useful types static_assert(std::is_arithmetic_v<T>, “Matrix template parameter type must be arithmetic”); using DataType = std::vector<T>; … Read more

## Right way to convert data.frame to a numeric matrix, when df also contains strings?

I have a data frame taken from a .csv-file which contains numeric and character values. I want to convert this data frame into a matrix. All containing information is numbers (the non-number-rows I deleted), so it should be possible to convert the data frame into a numeric matrix. However, I do get a character matrix. … Read more

## Rotate a Matrix in R by 90 degrees clockwise

I have a matrix in R like this: |1|2|3| |1|2|3| |1|2|3| Is there an easy way to rotate the entire matrix by 90 degrees clockwise to get these results? |1|1|1| |2|2|2| |3|3|3| and again rotating 90 degrees: |3|2|1| |3|2|1| |3|2|1| ? Answer t does not rotate the entries, it flips along the diagonal: x <- … Read more

## What techniques exists in R to visualize a “distance matrix”?

I wish to present a distance matrix in an article I am writing, and I am looking for good visualization for it. So far I came across balloon plots (I used it here, but I don’t think it will work in this case), heatmaps (here is a nice example, but they don’t allow to present … Read more

## Pandas: Creating DataFrame from Series

My current code is shown below – I’m importing a MAT file and trying to create a DataFrame from variables within it: mat = loadmat(file_path) # load mat-file Variables = mat.keys() # identify variable names df = pd.DataFrame # Initialise DataFrame for name in Variables: B = mat[name] s = pd.Series (B[:,1]) So within the … Read more

## Deprecation status of the NumPy matrix class

What is the status of the matrix class in NumPy? I keep being told that I should use the ndarray class instead. Is it worth/safe using the matrix class in new code I write? I don’t understand why I should use ndarrays instead. Answer tl; dr: the numpy.matrix class is getting deprecated. There are some … Read more

## Python Inverse of a Matrix

How do I get the inverse of a matrix in python? I’ve implemented it myself, but it’s pure python, and I suspect there are faster modules out there to do it. Answer You should have a look at numpy if you do matrix manipulation. This is a module mainly written in C, which will be … Read more

## How to use onSensorChanged sensor data in combination with OpenGL

( edit: I added the best working approach in my augmented reality framework and now also take the gyroscope into account which makes it much more stable again: DroidAR framework ) I have written a TestSuite to find out how to calculate the rotation angles from the data you get in SensorEventListener.onSensorChanged(). I really hope … Read more

## numpy subtract every row of matrix by vector

So I have a n x d matrix and an n x 1 vector. I’m trying to write a code to subtract every row in the matrix by the vector. I currently have a for loop that iterates through and subtracts the i-th row in the matrix by the vector. Is there a way to … Read more

## Iterating over Numpy matrix rows to apply a function each?

I want to be able to iterate over the matrix to apply a function to each row. How can I do it for a Numpy matrix ? Answer You can use numpy.apply_along_axis(). Assuming that your array is 2D, you can use it like: import numpy as np mymatrix = np.matrix([[11,12,13], [21,22,23], [31,32,33]]) def myfunction(x): return … Read more