Freehand Diagrams with Adobe Ideas

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Freehand diagrams have two big virtues: they are quick and they are unconstrained.

I used to use a notebook (see What are degrees of freedom) but recently I got an ipad and then I found Adobe Ideas. It’s completely free and has just the right level of complexity for getting ideas down fast.

A diagram for teaching machine learning

A diagram for teaching machine learning

It takes a bit of perseverance to get into a new habit but it pays off. Here are some examples and some tips on how to make it work as an alternative to paper.

First don’t bother using your fingers. You won’t have nearly enough control. Get a stylus. I use this one which is fairly cheap but works fine. I’ve noticed that it moves more freely when the ipad is in landscape position so I always draw with it that way round. I don’t know why this is but I guess it’s something to do with the glass.

The confusion matrix

The confusion matrix

Neighbourhood of C major

Neighbourhood of C major

When you first open Adobe Ideas it’s tempting to see the page in front of view as something that needs to be filled as you would a piece of paper. That’s the wrong way to approach it as you’ll get overly distracted by the task of orientating your work on the page. Instead treat the page as an enormous workboard. Start by zooming in somewhere in the middle and work outwards.

A diagram for teaching machine learning

A diagram for teaching machine learning

It’s vector graphic based so in principle infinitely deep. You’re only limited by how thin the pens get. Draw your diagram without any thought for the borders then right at the end scale it up to fit the page.

The next thing that might strike you is that there’s no copy and paste. Ideas is part of Adobe’s creative suite along with Photoshop and Illustrator and as such inherits their layer based approach to image editing. If you want to be able to adjust the positioning of parts of your diagram (say the key with respect to the rest of it) then you would be wise to put these on separate layers. You’d think this would be deeply frustrating however it’s one of those constraints that somehow makes you work better as you think more about your layout.

You are allowed 10 layers in total with one photo layer. I sometimes place an image of a grid on this layer if I need grid lines to work to.

If you are working quickly you don’t want to spending too much fretting about the colour palette. Again Ideas forces you into simplicity by limiting your colours to five at a time. Even better you can connect up to Kuler provided its app is also on your ipad. This gives you access to a huge range of palletes. The Kuler tool, which sucks the pallete out of an image, is also there by default in Ideas if you click on themes. This allows you to pull the colour scheme out any image on the photo layer.

Some Diagram Elements

Some Diagram Elements

When it comes to using the pen tool I tend to stick to the marker and constantly zoom in and out as I draw. I zoom right in for writing text and out again for drawing shapes. You soon get used to flipping between using your fingers to zoom and pan and your stylus to draw. It’s worth noting down the width of the pens you are using as it’s easy to get lose track of where you are and a diagram made up of many different line widths looks bad. I tend to use two widths: 6.5 and 3.

The toughest thing to pull off is anything that requires large scales swipes across the surface of the ipad, for example long straight lines or wide circles. It is easier to do this on a small scale with a thin pen and then enlarge the image.

One thing I didn’t realise for a while was that holding the pen tool for a few seconds in any completely circumscribed areas floods that areas with colour. This is very useful for filling shapes and creating colorful backgrounds.

I try to vary styles and colours although it takes an effort to keep this up if you are taking notes or in rush. I’ve listed in the panel on the left some of the diagram elements I’ve experimented with.

Adobe Ideas looks at first sight too limited to be particularly powerful but take a look at How to Use Adobe Ideas by Michael Startzman to see what is achievable by a professional!

A confused tangle

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A confusion matrix is a confusing thing. There’s a surprising number of useful statistics that can be built out of just four numbers and the links between them are not always obvious. The terminology doesn’t help (is a true negative an observation that is truly in the class but classified negative or one that is negative and has truly been classified as such!) and neither does the fact that many of the statistics have more than one name (Recall=sensitivity=power!).

To unravel it a little i’ve used the tangle js library to create an interactive document that shows how these values are related. The code can be found here.

The interactive example

I have trained my classifier to separate wolves from sheep. Let’s say sheep is a positive result and wolf is a negative result (sorry wolves). I now need to test it on my test set. This consists of wolves and sheep That&#8217s test subjects altogether.

Say my classifier correctly identifies sheep as sheep (true positives) and wolves as wolves (true negatives)

This gives us the confusion matrix below:

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Now some statistics that need to be untangled!

Precision (aka positive predictive value) is TP/(TP+FP). In our case /( + ) =

Recall (aka sensitivity, power) is TP/(TP+FN). In our case /( + ) =

Specificity is TN/(TN+FP). In our case /( + ) =

Negative predictive value is TN/(TN+FN). In our case /( + ) =

Accuracy is (TP+TN)/(TP+TN+FP+FN). In our case ( + )/( + + + ) =

False discovery rate is FP/(FP+TP). In our case /( + ) =

False positive rate (aka false alarm rate, fall-out) is FP/(FP+TN). In our case /( + ) =

Machine Learning and Analytics based in London, UK