As I’ve said before, bar charts are good for comparing distinct values. Unlike pie charts, which only need a minimum of two values to be informative, bar charts usually have more. Usually I wouldn’t think about a bar chart unless I had at least four values to compare. It’s hard to come up with an abstract example of when one would use a bar chart, so I’m going to share the story of and instructions for the first chart I ever created that made someone say “Wow, you can do that?”

# Monthly Archives: January 2011

# Charts: Adding context

Now, I’ve explained how to *create* various simple charts, but you may have noticed that there’s something all of my examples were missing.

Take for example, our basic pie chart. Imagine coming back to it a year or more after you made it. Do you remember what it’s about? How about when it was made? If so, you have a better memory (or make a lot fewer graphs) than I do! It really needs labels or a title or both to give it some sort of context. Without some sort of explanatory text, a graph is really just a picture (and not necessarily even a pretty one at that).

Most spreadsheet programs will allow you to add titles and labels both when the graph is first created, and later. If you have row/column labels next to the numbers you included in the graph, the program might even detect them and (try to) add them automatically for you. If it does try and manages to mess it up however, you can always fix it using the steps below.

Start by copying the table below and pasting it into your favorite program, then making a bar chart. Then follow the instructions for your program to turn your original graph into something that looks like this one, which was made in Excel 2007.

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# Line charts: Basic how-to

To make a line chart in a spreadsheet, all you strictly need to start with is a set of numbers. Line charts typically compare the values of several items — often but not exclusively the value of a single item at several different points in time. Most stock market charts are line charts with a *lot* of items.

Remember how I said on pie charts and bar charts that the order didn’t matter very much? It’s true, as long as they’re labeled correctly. (I’ll explain labeling later.) If you have 3 apples and 1 orange, that’s the same as having 1 orange and 3 apples. If Bob read 7 books and Sue read 9, that’s the same as if Sue read 9 and Bob read 7. Since we were comparing items that did not intrinsically have an order of their own it didn’t really matter what order they appeared in.

However, since line charts often compare values over time, all of a sudden it does matter. Let’s say that the values above were the number of fundraiser cookies sold each week. If you were to sort them in increasing order, then 23 would be first, followed by 35, etc. Unfortunately that puts week 5 first, followed by weeks 2, 3, 7, 1, 6, 4, and 8, in that order. For most purposes that just won’t work. Even if it were perfectly labeled, no-one would be able to read a chart like that at first glance. And since conveying information at a glance is what charts are for, that would defeat its purpose.

While you could theoretically make a line chart with only two items, it wouldn’t really look like one. The one pictured above was made with eight randomly generated values. If you want your line to look like mine you can copy the table below and paste it into your favorite spreadsheet.

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# Bar vs Column Charts: How to choose

Earlier, I said I’d discuss how to choose between bar charts and column charts. I make my choice based on three main considerations – subject, shape, and space.

# Bar charts: Basic how-to

To make a bar chart in a spreadsheet, all you strictly need to start with is a set of numbers. Bar charts typically compare the values of two or more items, although it could be argued that the iconic goal thermometer is an example of a single-item bar chart. For most purposes, however, you need a minimum of two items that you want to compare.

An example of this would be this simple chart, where the two numbers happen to be 1 and 3. If you had 25 and 75 you’d get almost the same chart, but the scale on the left axis would be different. The same would be true for 0.1 and 0.3. If you put them in a different order, however, the taller column would be on the left.

Ready to make a simple one? The first step is to enter the numbers. They should be in a column, and they can be any numbers you want, but to get a chart that looks like this one you’ll want to use 1 and 3, or some equivalent thereof. Then highlight them. After that, the steps depend on which program you’re using. Note that what I’m referring to as bar charts actually come in two styles — vertical (column) and horizontal. Which type you use depends on a variety of factors, which I’ll discuss later. For now, since these two types are essentially the same as far as how to do them, I will only explain how to do one kind per program.

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# Pie charts: Basic how-to

To make a pie chart in a spreadsheet, all you strictly need to start with is a set of numbers. Pie charts show the percentage of the whole, so at minimum for a reasonable pie chart you need 2 numbers, or two parts. An example of this would be this simple chart, where the two numbers happen to be 1 and 3. Note that these numbers don’t have to add up to 100 – the program will automatically figure out the percentages. If you had 25 and 75 you’d get the same chart, and the same would be true for 0.1 and 0.3. If you put them in a different order, however, the chart will still convey the same information, but it will look different.

Ready to experiment? The first step is to enter the numbers. They should be in a column, and they can be any numbers you want, but to get a chart that looks like this one you’ll want to use 1 and 3, or some equivalent thereof. Then highlight them. After that, the steps depend on which program you’re using.

Continue reading Pie charts: Basic how-to