# How to get statistics from an array Collection ? (min max, and average)

I have a text file that has a long 2D array as follows:

```[[1, 2], [5,585], [2, 0], [1, 500], [2, 668], [3, 54], [4, 28], [3, 28], [4,163], [3,85], [5,906], [2,5000], [6,358], [4,69], [3,89], [7, 258],[5, 632], [7, 585] ..... [6, 47]]
```

The first element of each has numbers between 1 to 7. I want to read information of second element for all and find the maximum and minimum amount for each group between 1 to 7 separately. For example output like this:

```Mix for first element with 1: 500
Max for first element with 1: 2
average: 251

Min for row with 2:  0
Max for row with 2:  5000
average: 2500

and so on
```

What is the most efficient way of getting min, max, and average values by grouping based on the first element of the array?

```file = open("myfile.txt", "r")

unique_values = set([list[1] for list in list_of_lists])
group_list = [[list[0] for list in list_of_lists if list[1] == value] for value in unique_values]

print(group_list)
```

We can use `pandas` for this:

```import numpy as np
import pandas as pd

file_data = [[1, 2], [5,585], [2, 0], [1, 500], [2, 668], [3, 54], [4, 28], [3, 28], [4,163], [3,85], [5,906], [2,5000], [6,358], [4,69], [3,89], [7, 258],[5, 632], [7, 585], [6, 47]]

file_data = np.array(file_data)

df = pd.DataFrame(data = {'num': file_data[:, 0], 'data': file_data[:, 1]})

for i in np.sort(df['num'].unique()):
print('Min for', i, ':', df.loc[df['num'] == i, 'data'].min())
print('Max for', i, ':', df.loc[df['num'] == i, 'data'].max())
temp_df = df.loc[df['num'] == i, 'data']
print("Average for", i, ":", temp_df.sum()/len(temp_df.index))
```

This gives us:

```Min for 1 : 2
Max for 1 : 500
Average for 1 : 251.0
Min for 2 : 0
Max for 2 : 5000
Average for 2 : 1889.3333333333333
Min for 3 : 28
Max for 3 : 89
Average for 3 : 64.0
Min for 4 : 28
Max for 4 : 163
Average for 4 : 86.66666666666667
Min for 5 : 585
Max for 5 : 906
Average for 5 : 707.6666666666666
Min for 6 : 47
Max for 6 : 358
Average for 6 : 202.5
Min for 7 : 258
Max for 7 : 585
Average for 7 : 421.5
```
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