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johan
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November 17, 2011

android

By Popular Demand – Reventer Detail View

November 17, 2011 | By | No Comments

Reventer users have been asking for a way to view Reventer data in more detail, or at a smaller interval.

Even though it’s always an option to send a csv file to Google Docs and further explore your data there, I agree that it would be good to be able to check out the details on your phone.
The image below is my first stab at figuring out how to make a detailed view for Reventer that will work well on a mobile phone.


Let me know what you think on google+

johan
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October 18, 2011

oracle

Introducing jiTree

October 18, 2011 | By | No Comments

I originally started work on jiTree as a way to improve my understanding of Oracle Indexes. Being a visual person, I often find that more complicated concepts are easier to master when I can see them visualised. So at it’s heart this is intended as an educational tool, to make understanding Oracle indexes more accessible.

A long term goal of the project is to improve the speed and accuracy of the visualisation to a degree where it can be used as a general purpose tool for investigating indexes, but whether this is practical (or can be accomplished in a browser) is not clear yet.
The key to jiTree
Using jiTree is simple. All you have to do is paste an Oracle Index Treedump into the box provided and hit the “Draw Index” button. Once drawn you can view and save an image of the visualisation by clicking the “View as Image” button at the bottom of the page.

Use jiTree

johan
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October 4, 2011

oracle

Oracle Index Tree Dump Visualisation

October 4, 2011 | By | No Comments

 Update: JiTree is an online tool for visualising your indexes.

I’ve been working on a Processing project to visualise Oracle Index Tree Dumps. This is a quick example of the progress. It’s still very much a work in progress, so there are problems to address.

For the test table I’m just copying the dba_objects view into a table.

SQL> select count(*) from dba_objects;

COUNT(*)
----------
68913

SQL> create table test_o as select * from dba_objects;

Table created.

SQL> create index test_o_idx on test_o(object_id);

Index created.

Next I get the treedump as follows:


SQL> select object_id
2 from dba_objects
3 where object_name = 'TEST_O_IDX';

OBJECT_ID
----------
71227

SQL> alter session set events 'immediate trace name treedump level 71227';

Session altered.

Plugging the treedump into my visualisation tool (as I said, it’s a work in progress) gives this view. A very simple tree consisting of only a root node (red) and leaf nodes (clustered around the yellow core).



Now I delete 20000 rows from the test_o table:

SQL> delete from test_o where object_id between 40000 and 60000;

19565 rows deleted.

SQL> alter session set events 'immediate trace name treedump level 71227';

Loading the new treedump shows us where leaf nodes have been deleted.


johan
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September 22, 2011

data visualisation

one tube minute

September 22, 2011 | By | No Comments

Click here to view the visualisation

When waiting on the platform a minute on the London Underground often feels longer than you’d expect. I decided to investigate this, and get some clarity on the length of one tube minute.

To do this I had to start by gathering the required data.

Data Gathering

Before I could record the duration of one minute according to the arrivals displays on the Underground, I needed to decide how I would measure this minute. Determining the start of the minute was easy. A minute starts when the arrival display switches to show that there is one minute remaining. The end of a minute was trickier to choose.

As far as I could tell there would be three options here:
- When the train enters the station
- When the train doors open
- When the train departs from the station

Because I wasn’t sure that I could always accurately record the point at which the train entered the station, and train departures can be delayed by people stuck in the tube doors, I chose to measure a minute as the time from when the arrivals display switches to one minute, and the time that the tube doors open.

With the method sorted I continued to record data using Reventer.

Visualisation

Having gathered the data I sent it to Google Docs (easy to do in Reventer) and started thinking about the best way to visualise this data. I’d recently read some good blogs about Processing.js, and having played with Processing in the past, I decided to use this to create the animation. I was also reading Nathan Yau’s Visualise This, which emphasizes using data to tell a story. To give readers the chance to experience the duration of the various tube minutes for themselves, I decided on using the animated balls to represent “minutes”.



johan
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June 21, 2011

android

Reventer Tutorial

June 21, 2011 | By | 3 Comments

At present Reventer is still in early development. For those who would like to use it and give feedback, here is a quick tutorial to get you started.

First Start

Until you have created at least one event, the first screen you will get when you start Reventer will look like this:



Click on the “add event” button to create a new event. An event is anything that can happen, like getting a headache, traveling somewhere or measuring something like a payment.

Adding an event

After you’ve clicked on the “add event” button you will be presented with a screen where you have to provide 2 details about the event:

  • What it is called
  • What type of event it is



    • There are three types of events available at the moment:

  • Timestamp – Any event for which you only want to record the time that it happened. Like keeping track of when you get headaches
  • Number – An event for which you want to record when it happened
    along with some numerical value, like your temperature or blood pressure (this doesn’t all need to be medical, and I’ll hopefully come up with some better examples soon)
  • Duration – Any event for which you want to record the duration, like the start and end times for a journey.



    After entering the name, just press the button identifying which type of event you are creating.

    Adding More Events

    To add more events, press the menu button on your phone or device, which will give you the option to manage events:



    Adding Event Instances

    Event instances refer to whenever an event actually happens.

    For timestamp events it is easy to add an event instance, just hit the big red + button next to the appropriate event. For our example using headaches, you would hit the + button every time you get a headache.

    IMPORTANT NOTE: Because events are grouped by either hours or days you will only have a dot to begin with. As you add more event instances over time your graph will get more interesting.

    For number events you will get a prompt to enter a value like below:



    To record a duration event instance, just push the play button next to the event.



    Once the event ends, you hit the stop button and the duration will be recorded in minutes.



    Grouping Event Instances

    This is where it gets interesting. Say you are keeping track of when you are getting headaches. It may be useful to get some idea of whether this is happening at certain times of day. This is where grouping comes in. To change what event instances are grouped by, just tap on the green graph on the main screen, and you will be presented with four options:



  • Hour: The event instances are grouped by the number of occurrences per hour, or, for number and duration events, by the number or duration of the event instance per hour
  • Day: The event instances are grouped by the number of occurrences per day, or, for number and duration events, by the number or duration of the event instances per day
  • Hour of Day: Here grouping is by the hour of the day in 24 hour format. Useful for seeing if event instances are occurring at specific times of day.
  • Day of Week: Here grouping is by the day of the week. Useful for seeing if event instances are occuring on specific days of the week


    • Exporting Events

    To export events wih all there instances you have two options. Either export to the SD Card(Export to CSV) or Export to any of your installed application on your Android device (send CSV).

    Once exported you have all the details of every recorded event instance.



    johan
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    June 7, 2011

    android

    Reventer 0.3

    June 7, 2011 | By | No Comments






    https://market.android.com/details?id=com.shockinggrey.reventer


    After some issues reported on earlier versions of Android (thanks bro), I’ve updated Reventer to 0.3 – now it works with any version of Android from 1.6 up. I even tested it on my G1.

    johan
    0

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    June 5, 2011

    android

    Reventer 0.1 Alpha Release

    June 5, 2011 | By | No Comments

    I’ve just released the first alpha version of Reventer to the Android Market. Whether anyone other than myself will find this useful remains to be seen, but I’m pretty happy with what Reventer can do, and this was always a project aimed at addressing my own requirements.

    Reventer (rapid event recorder) is a tool for data geeks to record when events occur and how often. By collecting data, Reventer helps you determine the empirical probability of events.

    Check it out on the Anrdoid Market.



    johan
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    April 23, 2011

    data visualisation

    massivedata on github

    April 23, 2011 | By | No Comments

    Nothing huge, but I’ve moved the massivedata demo to github. The project isn’t much more than the demo at the moment, but this is, if nothing else, a way to show my intent for massivedata as an open source project.

    https://github.com/ezuall/massivedata

    johan
    0

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    April 3, 2011

    android

    New Android App Icon

    April 3, 2011 | By | No Comments

    This week I did some work on the icon for my latest Android App. Contrary to my approach before I’ve decided to ignore the icon guidelines completely. After putting some work into following these guidelines, and providing a tutorial for other users to create Android icons which conformed to the original guidelines using Free and Open Source tools, the standard has been changed completely for Android 2.0+. Who’s to say that the standard won’t change in future?

    johan
    0

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    October 8, 2010

    data visualisation

    massivedata

    October 8, 2010 | By | No Comments



    Over recent years data visualisation has become a topic I really enjoy. Being a DBA, I’m used to trying to make sense of large volumes of data, but there is something extremely satisfying about the immediacy of a clear visual representation. What I was looking for is a tool that would always be available (home, work wherever) and that can handle very large amounts of data.

    That’s partly what sparked my interest in HTML5, which is promising a future with a blank canvas on every PC. From there my search took me to webgl (partly because of a game that I’ve been wanting to write for over a year now), and that’s when I had the idea for massivedata.

    The idea is to have an easy and clear way to visualise large amounts of data. Taking into account that webgl harnesses the power of the GPU, it seems to be the perfect fit for working with large-scale data visualisation.

    How it works

    You start off in heatmap mode. This corresponds to a top-down view in 3D space. Here values are represented by colour, and you have the advantage of seeing a very large amount of data at once.

    From heatmap mode you have the option of switching to a barchart view of either the columns or rows involved in the representation. A slider gives you control over which row/column you’re viewing, so you can compare values in different ways.

    Finally there is explore mode, in which you have a full 3D view of your dataset.

    This is still very much a work in progress, but find out how to get a webgl-capable browser, and then check out the demo.