The post Can you use this visualisation? appeared first on VeryViz.

]]>Interestingly, if you talk to a data analyst, you will find visualisation design is not simple. You will be told, it depends on the data and what you want to find out. The contradiction of the “user” is that they expect the visualisation to help them understand. Only after seeing a visualisation will they have an idea of what they might want to find out.

If you do not understand the purpose of a visualisation it simply becomes “eye candy”. Colourful pictures that suggesting something might be interesting.

We see this all too often with the graphs and graphics used in reporting and analysing COVID data. One visualisation example that got me really thinking it that presented and developed by (Three graphs …)

It is interesting to see graphs that shift the perspective, time is no longer an axis. However, the x-axis and y-axis are intrinsically inter-related. The x value is the rate of change of the y value. As a result we get curious graphs using the co-ordinate space in fascinating ways.

However, the dependence between x and y means when x is negative and line always descends and when it is positive it climbs. It is not easy knowing how to read this. It means each data source spirals upwards and downwards either side of the y-axis.

What to make of this visualisation? It seems to contradict the idea that it helps understand the data. The average number of deaths a day is not really a comparable scale across countries with differing populations, so the relative line positions are not that useful. The spiral patterns of each line are intrinsic to the data presentation approach. However the similarity of shape might be something of interest and that is easy to see. But what to make of one spiral that is squashed when seen next to another? Common dates cannot be easily related. There do seem to be “events” such as when spiral turns and starts again. But those events are not labelled on the graph, so we don’t know they show COVID restriction policy decision or a new variant appearing.

In fact to add to my confusion, what look like “events” might not be because of the poor representation of time. Imagine the y value stayed constant for a week before growing, and another stayed constant for nine weeks before growing. Both cases would appear the same!

One simple way of checking if you understand what is going on is to see if you can work the visualisation with some simple “known” data. In the graph style above: an unchanging value will be a dot with x at zero and some constant y value (the blue dot below). A consistently growing value will be a vertical line with a positive x (the green line below). A consistently dropping value will be a vertical line with a negative x (the red line below). A cyclic value such as temperature through 24 hours will be an ellipse (see the grey ellipse below).

These simple examples help us grasp what is being visualised. But they also show the challenges, a horizontal has no real meaning! Despite this, it is still hard to see what the particular visualisation of real COVID data is telling the viewer without sophisticated interpretative skills.

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]]>The post If you have an error, try #IFERROR appeared first on VeryViz.

]]>To avoid complete re-modelling your spreadsheet, “IFERROR” can be used effectively to trap errors so they do not disrupt your entire model. With the formula “=IFERROR(*F*,*G*)”, *F* is the computation you wanted to do and *G* is what you do if *F* gives an error.

G might a polite error message or value that avoids the annoyance of an error propagating through your model.

Watch this small illustration with a divide operation. You can see that when the first argument *F* is an error, the value from the second argument is used. If there is no error in the first argument, the second argument is ignored.

Of course if it just so happens that *G* gives an error it only shows when *F* is one too.

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]]>**You are following a workbook exercise using Excel. You’ve put the formula in, and entered the data. But something is wrong the number you’ve got is different to the workbook.**

**Option 1: You put your hand up. The class is interrupted and your learning is on hold until the tutor ends up working through the problem with you. It might be any number of issues.****Option 2: You check and re-write each bit of the formula, checking each bit as you go along. This takes quite a bit of time and of course you still might be making the same sort of mistake again and again. You might end up trying option 1!****Option 3: Your school has EQUS installed and running. Whenever a formula is selected, the breakdown of the computation with intermediate values is shown immediately. For example, you can see that the answer is wrong because a negation was missed. You edit the formula, make the correction and this time the answer is right and you see the slip is fixed. [You fixed it!]**

Naturally, option 3 will not fix every problem, the tutor may still need to help. However, some of the time getting stuck examining an error or mistake will be saved. Some learners will be able to see what is going on and fix it. And in that time, the tutor will be free help others who need more support.

One simple example of EQUS is if you select the formula =5-(0.26*3+0.34*2), it immediately shows:

Earlier we conducted an analysis comparing option 2 and option 3, shows time the saved with EQUS is dramatic. What we’ve not quantified is how EQUS helps independent learning, the tutor and the class as whole.

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]]>Numerical reasoning is often a challenge, especially when percentages are involved. To start with “%” is very simple, but of course its use in context often makes things harder. Here we show how putting percentage expressions in Excel and seeing them visualised in EQUS helps their comprehension.

It may seem trivial, the “%” is used after a number to show it is a percentage value. However, it is in fact a postfix operator which means “… now divide by 100″, with the number **before** the operator. As an operator “%” can be used any formula just like you might use “-” in front of an expression to negate it. Here’s 9% and -9% with the EQUS visualisation:

A simple example of how this can be a bit confusing would be “2/3%”. Now does that mean “2 divided by 0.03” or is it “0.6666 as a percentage (that would be 0.006666)”?

You can see the “%” takes precedence. If you know BODMAS, you will see there is no “P” for percentage. In fact it could or should be BPODMAS! So, to get the other result you need brackets:

Not to mention as an operator something like “sqrt(81)%%%%” is a valid expression meaning “the square root of 9 times 10^-8”.

Try EQUS and see if it helps untangle percentages for you, and much more.

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]]>The post For world refugee day … seeing now people have moved appeared first on VeryViz.

]]>Consider the forces at play that make someone, their family or even a child, pack-up and face the challenge of moving their live while under duress.

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]]>The post Free EQUS download for a limited period appeared first on VeryViz.

]]>EQUS provides an easy to use means of showing how Excel computations are performed. This help present mathematical workings to learners at a variety of levels and in many subject areas.

The same can be useful for anyone working with a spreadsheet when they’re not quite certain if the result shown is what they meant it to be.

Simply open the EQUS task pane and select the cell of interest. Immediately a visualisation is presented showing the computations and intermediate results.

Have a go … and use the discount code June2021 to ensure you get it for free.

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]]>The post Array formulae come to EQUS appeared first on VeryViz.

]]>*As people use EQUS more we come across interesting new requirement, here we describe how the visualisation has been enhanced for array formulae.*

An important improvement to EQUS is that it now visualises array formula. Array formula are formula for “power users”.

Imagine the common spreadsheet pattern: you copy a formula down a column to process a mass of data in rows. You use the same formula lots of times. Well a problem arises when you realise you need to update that formula. You have to change one version of the formula and make sure you copy and paste it again all the way down the row. Now that is easy, but it can lead to difficulties when the formulae are not documented. Poorly structured sheets, or someone else’s work or work you did years ago, all can make copying that new formula correctly rather hard.

Array formulae avoid this difficulty by allowing you to specify a formula overall the entire range of cells involved with just one expression. Once the expression is in place, the single array formula can be updated and it will immediately work across all the rows it involves. In a way this means that you end up being far more explicit with the cell inter-relations you want to compute. It also means you don’t have to rely on copying your formula correctly.

You can see when a formula is an array formula because it is shown the formula bar with curly braces around it. The braces are added by Excel, to enter an array formula you must press control-shift-enter. There is a lot more to array formulae, to find out more try searching using “excel array formula”, or “excel control-shift-enter” (see: Microsoft examples).

In our experience array formulae are a love hate thing. Those who have mastered them cannot believe how difficult life is without them. Others survive perfectly being disciplined with the copying of normal formulae.

Here’s an example of how they work, we’ve included the EQUS visualisation throughout to help show how things are working. We start looking at the copy and paste approach, here the need is to compute row 2 added to the product of rows 3 and 4. First we do it for the first column, column B:

This figure shows how a normal copy and paste solution starts. The requirement was for row 2 to be added to row 3 times row 4, and figure shows this for column B. That formula is them copied to all the required columns, C and so on. For C5 the formula looks like this:

It is this situation where the general requirement is lost. All those copies are different individual formulae that just happen to match. There is nothing linking them but for our knowledge that they should all hold that addition and multiplication formula. For example, the formula in column P could be changed and we’d never know until we spotted something that would make us check it.

The same addition and multiplication can be expressed in a array formula B2:V2+B3:V3*B4:V4. You can see the same pattern and operators, but the arguments are the range expressions for all the columns required. This captures the entire general requirement in one formula. To enter it into the spreadsheet first select the range of cells that are to hold the answers (in this example the light blue ones, B5:V5), then entering =B2:V2+B3:V3*B4:V4 and then pressing control-shift-enter.

The formula bar now shows:** {=B2:V2+B3:V3*B4:V4} **– the curly brackets show the formula is an array.

Cells B5 and C5 are shown below.

You see in these figures that the formula is exactly the same formula associated with each cell in the result range. By contrast to help judge that things are working as planned, the EQUS visualisation shows the formula and for any individual cell it shows the computation broken down. So you can see the general view given by the formula and the individual cases given by the data in any one element.

Array formulae do not have strictly line up, this allows more interesting expressions to be used. For example, for the figures computed row 5 we might need to see the differences between each column. This can be done by computing the difference between B5 and C5, C5 and D5, and so on. For just B5 and C5 the difference would be absolute value of one subtracted from the other: abs(B5-C5).

The cut and paste solution would be copy this across all the columns needed. But the array formula captures it completely in one: abs(B5:S5-C5:T5). Notice how one input range starts at B and runs to S, while the other starts at C and runs through to T.

Again the EQUS visualisation helps you see if it is doing what you want, by showing the formula and also the specific cases. Below shows C7:

Array formula are in a way a shift to using more programming-like constructs within a spreadsheet. The simple examples are the most compelling but in general they can be used to harness significant power and efficiency. They can work across rows, columns and areas.

Interestingly Microsoft are now providing more powerful approaches to arrays of data with their dynamic array formulae. The principles they follow are much the same as the array formula discussed here.

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