## How can I , using Numpy, compute how many entries in my array that gives the cumulative sum of 0,9 as an example?

After preforming PCA I have my (rescaled and proportion of variance explained) array with the sum 1.
I have to many components to get a good screeplot - therefore I would like to be able to somehow set the desired cumulative sum and get how many of the components of the array I will need to get it.
As an example `[0, 1, 2, 3, 4, 5]`

and I wanted the cumulative sum of 6 I'd get the answer that I'd need four entries.

My solution would be to use `numpy.cumsum`

together with `numpy.where`

:

arr = np.arange(6) # dummy data max_cum = 6 # your stop certerion arr_cum = arr.cumsum() # calculate cumulative sums of your array num = np.where(arr_cum >= max_cum) # get indices where arr_cum passes your max_cum >> In: num[0][0] >> Out: 3

`num`

contains all indices which contain values that are equal to or higher than your stop criterion, so you will need to fetch the first one (`numpy.where`

returns a 2D-array, so you will need `[0][0]`

).

One-liner function:

def lowest_cum(arr, max_cum): return np.where(arr.cumsum() >= max_cum)[0][0] >> In: lowest_cum(arr=np.arange(6), max_cum=6) >> Out: 3

Edit: needless to say that you need +1 for the number of entries, as the function will return the first index at which the cumsum is completed, so index 3 means 4 entries.

**numpy.cumsum — NumPy v1.19 Manual,** I have to many components to get a good screeplot - therefore I would like to how many entries in my array that gives the cumulative sum of 0,9 a As an example [0, 1, 2, 3, 4, 5] and I wanted the cumulative sum of 6 I'd get� numpy.sum(arr, axis, dtype, out): This function returns the sum of array elements over the specified axis. Parameters : arr : input array. axis : axis along which we want to calculate the sum value.

You can calculate the cummulative sum, and then calculate the `.argmax(..)`

where it is greater than or equal to the threshold:

>>> np.argmax(np.hstack((a.cumsum() >= 6, True))) + 1 4

Since `a.cumsum()`

is the cummulative sum, and thus:

>>> a.cumsum() array([ 0, 1, 3, 6, 10, 15])

and we thus calculate the first index where the threshold is satisfied:

>>> a.cumsum() >= 6 array([False, False, False, True, True, True])

We append a `True`

, such that in case there is no equence satisfying the threshold, it will return the number of elements *plus* one.

**numpy.cumsum() in Python,** Sum array elements. trapz. Integration of array values using the composite trapezoidal rule. diff. Calculate the� 1 How can I , using Numpy, compute how many entries in my array that gives the cumulative sum of 0,9 as an example? Feb 12 1 Getting the column “number” and column name to make it easier to select several - not always adjacent - columns in a large df in pandas Oct 23 '19

Assuming `a`

is already sorted, simply count the number of entries which do **not** yet exceed the threshold, and add the final entry which does.

a = np.arange(6) num = (a.cumsum() < 6).sum() + 1 # 4

As a function:

def cum_thresh(a, thresh): """ the sequence a has to be sorted """ return (np.cumsum(a) < thresh).sum() + 1

**Python program to find Cumulative sum of a list,** axis : Axis along which the cumulative sum is computed. unless arr has an integer dtype with a precision less than that of the default Input array : [[2 4 6] [1 3 5]] cumulative sum of array elements taking axis 1: [[ 2 6 12] [ 1 4 9]] also write an article using contribute.geeksforgeeks.org or mail your article� In older versions you can use np.sum(). In np.sum(), you can specify axis from version 1.7.0. Check if there is at least one element satisfying the condition: numpy.any() np.any() is a function that returns True when ndarray passed to the first parameter conttains at least one True element, and returns False otherwise. numpy.any — NumPy v1.16

**numpy.cumsum() in Python,** How to compute natural, base 10, and base 2 logarithm for all elements in a given array using NumPy? Python Collections Module. Most visited� 3 How can I , using Numpy, compute how many entries in my array that gives the cumulative sum of 0,9 as an example? Feb 12 3 Fortran: add column to file (i.e. skip a varying amount of horizontal spaces) Jun 11 '14

Python numpy cumsum() function returns the cumulative sum of the elements Let's look at some examples of calculating cumulative sum of numpy array elements. Cumulative Sum of elements at 0-axis is: [[ 1 2] [ 4 6] [ 9 12]] Cumulative Sum of I love Open Source technologies and writing about my experience about� NumPy package contains an iterator object numpy.nditer. It is an efficient multidimensional iterator object using which it is possible to iterate over an array. Each element of an array is visited using Python’s standard Iterator interface. Let us create a 3X4 array using arange() function and iterate over it using nditer. Example 1

NumPy - Array Attributes. In this chapter, we will discuss the various array attributes of NumPy. ndarray.shape. This array attribute returns a tuple consisting of array dimensions. It can also be used to resize the array. Example 1

##### Comments

- I didn't get the one-liner to work but the code above worked like a charm. Thanks! Or should I say: Tack så mycket!
- You can call the function like
`lowest_cum(arr=np.arange(6), max_cum=6)`