Line Graph



Four common graphs and chartsLine GraphBar ChartPie ChartX-Y Plot (Scatter Graph)Even before we’d computer software to draw graphs and charts quickly and accurately (like Excel), people took the time to do so by hand. This is because we’re not good at spotting patterns in data when it’s just pages and pages of numbers.Many tasks involve working with lots of numbers (like measurements taken over time). If you turn those numbers into the right graph or chart it makes it much easier to try and spot what is going on e.g. is there a pattern that repeats, how is something changing. Example: Post Operation MonitoringLine graphs are used to track body temperatureAn example would be monitoring the body temperature and the heart rate of a patient after they’ve had a medical operation.Humans are warm blooded animals and our bodies are constantly working to maintain a constant temperature (e.g. if your body temperature rises you start to perspire to cool down).This is different to cold blooded animals like lizards whose body temperatures vary. A big concern in hospitals is that a patient who has just had a medical procedure (an operation) might contract an infection.A rise in a patient’s temperature after surgery can be an indication that they have an infection. Here are the recorded temperatures for a patient who returned from surgery at 13:00. It’s tracked every 15 mins for the first hour, then every 30 mins.Time13:0013:1513:3013:4514:0014:1514:3014:45Temp 37.037.036.836.836.937.5Time15:0015:1515:3015:4516:0016:1516:3016:45Temp 37.037.137.036.8Time17:0017:1517:3017:4518:0018:1518:3018:45Temp 36.537.037.2It’s not easy to see how many of the readings were outside the normal range of 36-37 degrees Celsius.Instead of having to look at a rows of numbers, if they are plotted on a line graph, it’s easier to see if the patient’s temperature it’s staying more or less the same or if something else is happening.Why are there so many types of graphs and charts?We can be fooled by camouflage but we are good at spotting movement. It’s probably a Darwinian trait that was useful for our survival. We could see predators (and prey) when they moved. This may be why we are much better at spotting visual cues like patterns or changes when they are in a diagram than just looking at rows and columns of numbers. Over the years people have come up with different ways to organise the numbers they are working with (the raw data) into something visual that makes it easier to spot patterns and help them work out what’s going on in a situation. Some of the graphs and charts they came up with turned out to be so useful that they ended up getting used again and again.Once we had affordable computers with visual displays (and printers), those were the ones that were included in spreadsheet software (like Excel). Line GraphBar ChartPie ChartX-Y Plot (Scatter Graph)How do I choose which type of graph to use?Line graphs are useful to track changes over short and long periods of time.You can see over a period of time if something is increasing, decreasing staying the same or if it’s repeating some kind of cycle e.g. shops would expect higher sales just before Christmas You usually put time along the x axis (the horizontal one).Bar charts are used to compare things between different groups.They can also be used to show something changing over time if it’s something you measure over a fixed period (e.g. annual sales, how many times you went jogging in a month) where you have to wait until the end of the year or month before you can add a new bar.Pie charts are good when you are trying to compare parts of a whole thing e.g. out of your total sales, what do you sell the most of or out of the total time you spend working, which tasks eat up most of your time.Pie charts do not show changes over time. You’d need two pie charts showing the information at different times to show that kind of change.X-Y plots (scatter graphs) are used to study the relationship between two different things. Sometimes the points don’t appear to follow any pattern – there may not be a relationship - but if there is, a scatter graph can help you spot situations where there might be a link.If both things seem to increase at the same time, we say that they might have a positive correlation.If one decreases while the other increases, they have a negative correlation. ................
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