SQL By Parts

Twitter Clients for Android

Martin Cairns — Sat, 04 May 2013 18:37:07 +0000

Since Tweetdeck is going to stop working in a couple of days I’ve decided to install virtually all of the Twitter clients on the Google Play market place and eliminate them one by one until I’ve got a client which matches all my requirements.

Requirements

Customisation of font size and theme colours (I want a dark background and small fonts)
Custom columns i.e. not just Twitter stream, mentions & Direct Messages (I want to be able to have #SQLHELP as a first class column)
Ability to filter tweets based on keywords and source twitter client (Helps to filter out noise about whatever type of sportball people like to whitter on about, anything from paper.li and also filter out automated spam like paper.li)

Disclosure

I’m currently using Plume has it was the first client which met my requirements but I want to make sure that their isn’t another client out there with a killer feature that I’ve not seen. Another client I like the look of is TweetLines and for which I’m close to paying the price for the premium features to see how it faces off against Plume.

On the PC I’m using MetroTwit Beta as my TweetDeck 0.38.2 replacement, as after going through the customisation options I got it setup the same as I had TweetDeck.

Applications in order of rejection

1) HashTweet

Looked interesting but I wasn’t able to scroll through the list of tweets, this is a fatal bug so I’m crossing this one off the list first. It’s unique feature of analysing your twitter feed for different Hash Tags might of been useful, I guess I need to request this as a feature from the twitter client selected.

2) Stream Life

Combines Twitter, Facebook, Telephone calls and SMS into one stream or split out individually. It doesn’t support Twitter searches or any real customisation of the interface so this one is out as well.

3) Echofon

Has the dark theme and font customisations I wanted but doesn’t support adding custom columns. It’s support for conversation threads is also poor requiring two presses to see the previous messages even though the screen in the middle has plenty of empty space to show the rest of the thread.

Partitioning Slidedeck and Demos

Martin Cairns — Fri, 22 Feb 2013 13:29:47 +0000

Just a quick post to put up the links to slide deck and demos for partitioning presentation Partitioning Slide deck & Partitioning Demos.

Analysing and Refactoring a Recursive Function

Martin Cairns — Sun, 08 May 2011 18:15:19 +0000

At SQL Bits the wonders of networking in the SQL community showed it benefits, in a conversation with Jen Stirrup and Chris Testa-O’Neill mentioned that I was a math expert (his words not mine); later on Jen was talking to Chris Webb and he mentioned a problem he was with the performance of a recursive formula in Analysis Services and she then pointed him in my direction.

I was able to transform the recursive formula to one just based on Product and Sum of the values. Since I believe that a lot of Analytic systems start life in an excel spread sheet, so I decided to write-up some of the steps in the process of analysing and transforming these formulas.

The recursive formula in question is where is either 1 for a Long Position or -1 for a Short Position for the period t and is the percentage Profit or Loss for the period t.

Before I start the analysis it going to be helpful to give some examples of the values

Example 1: Long Position with 10% growth per period

Period	1	2	3	4
LS	1	1	1	1
RoR	0.1	0.1	0.1	0.1
CRoR	0.1	0.21	0.331	0.4641

Example 2: Short Position with 10% profit per period

Period	1	2	3	4
LS	-1	-1	-1	-1
RoR	0.1	0.1	0.1	0.1
CRoR	0.1	0.19	0.271	0.3439

Example 3: Swapping Long and Short Positions



Period	1	2	3	4
LS	1	-1	1	-1
RoR	0.1	0.1	0.1	0.1
CRoR	0.1	0.19	0.309	0.3781
Period	1	2	3	4
LS	-1	1	-1	1
RoR	0.1	0.1	0.1	0.1
CRoR	0.1	0.21	0.289	0.4179

As with all recursive formulas the end points have to be defined and they’re .

The first step was to factor the formula to reduce the number of terms giving

The next step is to shorten the names of the terms to save space when expanding the formulas.

Now we will look at the expansion of the first couple of terms to get an idea of the shape of the formula.

A pattern has emerged so it easy to see that for we will have followed by until which will have the term from 3 to 5.

This is starting to look like the expansion of a simple series since the common term is a good place to start finding solution will be to set to allow the analysis on the simplified formula.

The product of our simplified term for period 4 is expanding and collecting the terms gives us substituting the approximated gives us back which is the same pattern as the formula for except for the 1 at the start of the formula and the fact that we’ve ignored by setting it to 1 for all values.

Since the full definition for means that there will be no terms with without a matching . We will need to find a function to apply to the generated formula to remove the leading 1 and the where required.

There are two methods we can use either we choose simple values to place in the formula which would be the numerical analysis of the formula or we can perform the same algebraic analysis we have used to get to this point.

Using the function for the first couple of terms gives us

To get we need to divide by itself and times by which is