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What can we learn from looking at a group of numbers?
What can we learn from looking at a group of numbers?
In Machine Learning (and in mathematics) there are often three values that interests us:
Example: We have registered the speed of 13 cars:
speed = [99,86,87,88,111,86,103,87,94,78,77,85,86]
What is the average, the middle, or the most common speed value?
The mean value is the average value.
To calculate the mean, find the sum of all values, and divide the sum by the number of values:
(99+86+87+88+111+86+103+87+94+78+77+85+86) / 13 =
89.77
The NumPy module has a method for this. Learn about the NumPy module in our NumPy Tutorial.
Use the NumPy mean() method to find the
average speed:
import numpy
speed = [99,86,87,88,111,86,103,87,94,78,77,85,86]
x = numpy.mean(speed)
print(x)
The median value is the value in the middle, after you have sorted all the values:
code.strong { border-bottom: 3px double red; color:red; font-size:150%; } .darktheme code.strong { border-bottom: 3px double #88c999!important; color:#88c999!important; } code.underlined { border-bottom: 1px solid red; color:red; } .darktheme code.underlined { border-bottom: 1px solid #88c999!important; color:#88c999!important; }
77, 78, 85, 86, 86, 86, 87, 87, 88, 94, 99, 103, 111
It is important that the numbers are sorted before you can find the median.
The NumPy module has a method for this:
Use the NumPy median() method to find the
middle value:
import numpy
speed = [99,86,87,88,111,86,103,87,94,78,77,85,86]
x = numpy.median(speed)
print(x)
If there are two numbers in the middle, divide the sum of those numbers by two.
77, 78, 85, 86, 86, 86, 87,
87, 94, 98, 99, 103
(86 + 87) / 2 = 86.5
Using the NumPy module:
import numpy
speed = [99,86,87,88,86,103,87,94,78,77,85,86]
x = numpy.median(speed)
print(x)
The Mode value is the value that appears the most number of times:
99,86, 87, 88, 111,86, 103, 87, 94, 78, 77, 85,86 = 86
The SciPy module has a method for this. Learn about the SciPy module in our SciPy Tutorial.
Use the SciPy mode() method to find the
number that appears the most:
from scipy import stats
speed =
[99,86,87,88,111,86,103,87,94,78,77,85,86]
x = stats.mode(speed)
print(x)
The Mean, Median, and Mode are techniques that are often used in Machine Learning, so it is important to understand the concept behind them.