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Jon Fletcher

Creating a Python function to calculate Pi

Pi is 3.14159 to 5 decimal places.
To work out Pi, we will be using Leibniz’s formula:
X = 4 – 4/3 + 4/5 – 4/7 + 4/9 – …
This series converges to Pi, the more terms that are added to the series, the closer the value is to Pi.
For the proof on why this series converges to Pi – https://proofwiki.org/wiki/Leibniz’s_Formula_for_Pi
There are several points to note about the series:

  • It’s infinite, we need to find a way to continue adding term after term.
  • The denominator of the fraction increases by 2 every term.
  • The terms alternate between positive and negative.

Firstly, let’s create a function called pi.

To continue adding terms, let’s use a for loop. Every time the loop executes another term is added.

range(1,10) will produce the numbers 1, 2, … 9, 10.
However, before the loops starts, our variables’ initial values need to be set.

The pi series will start from 0.
n represents the numerator of our fractions which is the constant 4.
d represents the denominator of our fractions which starts as 1.

d needs to increase by 2 every loop, let’s use sum equals to do this.
Pi will also use a sum equals, a denotes our positive/negative function which we will get on to:

The only problem left is how to get a to alternate between 1 and -1.
This is where we introduce modulo.
Modulo outputs the remainder of a division and is denoted by %.

This example shows from numbers 1 to 4, modulo 2 alternates between 0 and 1.
If we multiple by 2 and minus 1 it will alternate between 1 and -1 which is what we require.

Putting everything together gives:

This isn’t close to 3.14159 at all.


However, we are only executing the loop 10 times, hence only 10 terms are being used to calculate Pi.

Increasing the number of loops to a million will change this:

There it is! A function written from scratch to calculate Pi.
To get a value even closer to Pi just increase the number of loops.

Finally, if you do wish to use Pi in python the easiest way is to use the numpy library, which has a pi constant stored.

Creating Power BI Layouts using PowerPoint

First question, why bother with layouts?
Using layouts in Power BI allows a user to make their visuals stand out better, the page looks professional and more appealing to its audience.

Second question, why PowerPoint?
The default page size in Power BI desktop is 16:9, (this trick doesn’t work for other Power BI page sizes), which is identical to a PowerPoint slide.
Therefore whatever is designed in PowerPoint will fit onto a Power BI page perfectly. Also PowerPoint is very easy to use; most people are familiar with it.

You’ll need a Power BI dashboard that you want to add a layout to. I’ll be using a dashboard displaying data on the Premier League top 50 goals scorers.

To start the creation of a layout, open PowerPoint with a blank side and add a rectangle.

Next, add glow to the rectangle, glow is found in the drawing ribbon under shape effects.

Repeat the process of adding rectangles with glow and lay them out so the visuals will fit.

If there is an important visual that needs to be a certain size you can find the size of the visual in Power BI in pixels and tailor the rectangle size to your visual.
Unfortunately PowerPoint displays sizes in cm so the numbers will need converting.
I use the following – https://www.unitconverters.net/typography/pixel-x-to-centimeter.htm

Once happy with the layout, save the slide as a PNG file. Upload this as the background in Power BI by going to format then page background, then selecting your created PNG file.

There you go!! A Power BI dashboard with its own custom layout.

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The Frog Blog

Team Purple Frog specialise in designing and implementing Microsoft Data Analytics solutions, including Data Warehouses, Cubes, SQL Server, SSIS, ADF, SSAS, Power BI, MDX, DAX, Machine Learning and more.

This is a collection of thoughts, ramblings and ideas that we think would be useful to share.

Authors:

Alex Whittles
(MVP)
Reiss McSporran
Jeet Kainth
Jon Fletcher
Nick Edwards

Data Platform MVP

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