Finding percentage change with Numpy

## Finding percentage change with Numpy

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numpy diff
numpy percentage of total
numpy difference between two arrays
pandas percentage
pandas pct_change fill_method
pandas percent change between two columns
numpy percentile

I'm writing a function to find the percentage change using Numpy and function calls. So far what I got is:

```def change(a,b):
answer = (np.subtract(a[b+1], a[b])) / a[b+1] * 100

print(change(a,0))
```

"a" is the array I have made and b will be the index/numbers I am trying to calculate.

For example:

My Array is

```[[1,2,3,5,7]
[1,4,5,6,7]
[5,8,9,10,32]
[3,5,6,13,11]]
```

How would I calculate the percentage change between 1 to 2 (=0.5) or 1 to 4(=0.75) or 5,7 etc..

Note: I know how mathematically to get the change, I'm not sure how to do this in python/ numpy.

If I understand correctly, that you're trying to find percent change in each row, then you can do:

```>>> np.diff(a) / a[:,1:] * 100
```

Which gives you:

```array([[ 50.        ,  33.33333333,  40.        ,  28.57142857],
[ 75.        ,  20.        ,  16.66666667,  14.28571429],
[ 37.5       ,  11.11111111,  10.        ,  68.75      ],
[ 40.        ,  16.66666667,  53.84615385, -18.18181818]])
```

Whats the most pythonic way to calculate percentage changes on a , The side effect is that calculations look a lot simpler. With numpy, you create an array for your data >>> import numpy as  numpy.percentile() Percentile (or a centile) is a measure used in statistics indicating the value below which a given percentage of observations in a group of observations fall. The function numpy.percentile() takes the following arguments. numpy.percentile(a, q, axis) Where,

I know you have asked this question with Numpy in mind and got answers above:

```import numpy as np
np.diff(a) / a[:,1:]
```

I attempt to solve this with Pandas. For those who would have the same question but using Pandas instead of Numpy

```import pandas as pd
data = [[1,2,3,4,5],
[1,4,5,6,7],
[5,8,9,10,32],
[3,5,6,13,11]]

df = pd.DataFrame(data)
df_change = df.rolling(1,axis=1).sum().pct_change(axis=1)
print(df_change)
```

Python, Pandas pct_change() method is applied on series with numeric data to calculate Percentage change after n number of elements. By default, it calculates  So using the freq argument you can find the percentage change for any timedelta values, Suppose using this dataframe you want to find out the percentage change after every 5 days then set the freq as 5D. The first five rows is NaN since there are no 5 days back data is present for these values to find the pct change.

```import numpy as np
a = np.array([[1,2,3,5,7],
[1,4,5,6,7],
[5,8,9,10,32],
[3,5,6,13,11]])
np.array([(i[:-1]/i[1:]) for i in a])
```

np.diff - Numpy and Scipy, The simple daily percentage change in closing price (without dividends and other factors) is the percentage change in the value of a stock over a single day of. Basically it gives the indices of the N smallest and largest values along the given axis of a numpy array. Find indices of N smallest values in a Numpy array . Let’s take the same original array. 1. arr = np. array ([69, 38, 60, 91, 4, 81, 54, 45, 13, 9

Calculating the simple daily percentage change in closing price , This is useful in comparing the percentage of change in a time series of elements​. Parameters. periodsint, default 1. Periods to shift for forming percent change. When the NumPy package is loaded, ndarrays become as much a part of the Python language as standard Python data types such as lists and dictionaries. To load NumPy, import the NumPy module: >>> from numpy import * >>> This allows NumPy functions to be used without qualifying them with the prefix numpy. Alternatively, if NumPy names might

pandas.DataFrame.pct_change, So you are interested to find the percentage change in your data. Well it is a import pandas as pd import random import numpy as np df = pd. We would like to show you a description here but the site won’t allow us.

How to find Percentage Change in pandas, Percentage change between the current and a prior element. The pct_change() import numpy as np import pandas as pd. In :. s = pd. This tutorial video covers how to calculate percent change within Python. The idea of percent change is usually to normalize a line for comparison of topics or to measure growth easily.