Types of Graphs



Types of Graphs

There are a number of major styles you can choose from when creating a graph. The style you choose implies some things to your readers.

  

Error graphs display not only a Y-value for each X-value, but a range of Y-values for a given X-Value. Error graphs are typically used to display the variation of each data point around its central value. For each X value in an Error graph, there is an associated Y value and an ``error range'' value that represents the deviation from the Y value. Just as with line and bar charts, Error graphs can show multiple sets of data.   

Hi Lo graphs display not only a Y-value for each X-value, but a range of Y-values for a given X-Value. Hi Lo graphs are typically used to display error bars or the trading range of a stock and its closing value for each period. The range of Y-values represent the low, standard (closing), and the high values for the given X value.   

Like Hi Lo graphs, Box graphs display not only a Y-value for each X-value, but a range of Y-values for a given X-Value. Box graphs are typically used to display the upper and lower variances associated with each Y value. This variance range is displayed as a rectangle. The median point can also be marked. You can even fill in the High and Low Y data ranges to combine a Hi Lo and a Box graph.   

Like Hi Lo and Box graphs, Westinghouse graphs display multiple Y-values for each X-value. Westinghouse graphs, however, display two different Y-values in separate plots which share the same X axis but have different Y axes. Westinghouse graphs are typically used to display the mean and variance of the Y value over a range of X values.   

|Think about an inquiry project that your students might engage in| |

|within your domain. When would you use this graph? What data | |

|would you need to have? | |

|Write 2 questions that you could ask your classmates to test if | |

|they understand what this graph means. | |

[pic]

| |Area Charts |

| |Area charts show the relative contributions over time that each |

| |data series makes to a whole picture. For example, an area chart |

| |would be good to show how much the relative amounts of the |

| |principal and interest change over time of a mortgage. |

|Think about an inquiry project that your students might engage in| |

|within your domain. When would you use this graph? What data | |

|would you need to have? | |

| | |

|Write 2 questions that you could ask your classmates to test if | |

|they understand what this graph means. | |

| | |

| | |

| | |

[pic]

|[pic] |Line Graphs |

| |Line graphs are used to plot various types of X-Y data. In its |

|[pic] |simplest form, a line graph is nothing more than a set of data |

| |points on an X-Y grid, possibly connected by line segments. |

| | |

| |A line chart plots the value of the variable as a specific point,|

| |then 'connects the dots' in order to give you some idea of the |

| |relationship of consecutive points. |

| |Line charts may also be used to show how the value of a variable |

| |changes over time. Unlike bar and column charts, line charts |

| |imply continuous change rather than a number of discrete points. |

| |For this reason, line charts are better at implying a trend. For |

| |example, if you are doing an experiment about the number of fish |

| |in a certain pond, you might be interested in the number of fish |

| |in the pond at a certain time, but you may also be very concerned|

| |with the trend of the fish population. Is it increasing or |

| |decreasing? |

| |Just because a line chart implies trends does not necessarily |

| |mean they are there! Be careful when interpreting such charts |

| |that you do not automatically assume intermediate values by the |

| |line placement. |

| | |

| | |

|Think about an inquiry project that your students might engage in| |

|within your domain. When would you use this graph? What data | |

|would you need to have? | |

| | |

|Write 2 questions that you could ask your classmates to test if | |

|they understand what this graph means. | |

| | |

| |[pic]plot data values much like a line graph except that a bar is|

| |drawn from the X axis to the Y value for the data. The points |

| |associated with different sets of data are grouped by their |

| |X-axis label to permit easy comparison between groups. Each set |

| |of data is represented by a different color or pattern. |

| |Column charts are like bar charts because they compare distinct |

| |items or show single items at distinct intervals. However, column|

| |charts have the categories arranged along the horizontal axis and|

| |the values along the vertical axis, so the bars are vertical on |

| |the chart. |

| |A very common use for column charts is to display how values |

| |change over discrete units of time (monthly or yearly change, for|

| |example). |

| | |

| |Bar charts compare distinct items or show single items at |

| |distinct intervals. Usually, a bar chart is laid out with |

| |categories along the vertical axis and values along the |

| |horizontal axis. In other words, the bars are horizontally placed|

| |on the page. Bar charts are useful for comparing data items that |

| |are in competition, so it makes sense to place the longest bars |

| |on top and the others in descending order beneath the longest |

| |one. |

|Think about an inquiry project that your students might engage in within your domain. When would you use this graph? What data | |

|would you need to have? | |

| | |

| | |

|Write 2 questions that you could ask your classmates to test if they understand what this graph means. | |

| | |

| | |

|   [pic] Stacked Line and Stacked Bar graphs work exactly like the non-stacked versions except that the Y values from previous | |

|data sets are accumulated as each new data set is plotted. Thus, bars appear to be stacked upon each other rather than being placed| |

|side-by-side. | |

[pic]

[pic]

|[pic] |[pic] |

| |Pie charts show the percentage that each data item contributes to|

| |the sum of all the data items. The cells of the X Range specify |

| |the labels for the slices of the pie while those of the Y Range |

| |indicate the value of the item. The percentages are calculated |

| |automatically. |

| |A pie chart is used to show proportions of a whole. It is very |

| |useful for figures that relate to a larger sum, such as |

| |demographic data or budget information. It is easy to get a feel |

| |for the relationship between component values when they are |

| |placed in a pie chart. Be careful that you do not have too many |

| |slices in the pie, or they will become meaningless. |

| |Also, note that a pie chart is usually used as a snapshot of ONE |

| |moment in time. If you want to show relationships as part of a |

| |whole over time, you would use an area chart. If you want to look|

| |at a number of pie charts at once, you might consider a doughnut |

| |chart. |

|Think about an inquiry project that your students might engage in| |

|within your domain. When would you use this graph? What data | |

|would you need to have? | |

| | |

|Write 2 questions that you could ask your classmates to test if | |

|they understand what this graph means. | |

| | |

| | |

| |[pic] |

| | |

| |A scatter plot is the simplest type of graph. It simply plots the|

| |data points against their values, without adding connecting |

| |lines, bars or other stuff. This is visually the least appealing |

| |type of graph, but the lack of bells and whistles can actually be|

| |an advantage. Since all the other types of graphs tend to have |

| |some kind of psychological implication built in (eg bar charts |

| |imply comparison, line graphs imply continuity), scatter diagrams|

| |are devoid of this type of clutter. If you are searching for the |

| |patterns and meaning in a graph, you may find the scatter diagram|

| |the clearest representation of the data. Once you understand what|

| |it means, you can use one of the other types of graph to give |

| |your readers whichever impression you choose. |

|Think about an inquiry project that your students might engage in| |

|within your domain. When would you use this graph? What data | |

|would you need to have? | |

| | |

|Write 2 questions that you could ask your classmates to test if | |

|they understand what this graph means. | |

| | |

| | |

| | |

[pic] A histogram graph the distribution of a set of points. The range of the values specified by the X Range are divided in sub-ranges called bins. The count of the number of items within each sub-range is displayed. You indicate the number of bins by setting the number of tick marks for the X axis. You can also set the range of data using the Max and Min entry boxes in the X-Axis Options dialog box.

   [pic]

| | |

| | |

|Think about an inquiry project that your students might engage in| |

|within your domain. When would you use this graph? What data | |

|would you need to have? | |

| | |

|Write 2 questions that you could ask your classmates to test if | |

|they understand what this graph means. | |

| | |

| | |

| | |

| | |

| |[pic] |

| |Many of the above charts can be created in 3-dimensional forms. |

| |The charts work pretty much the same way, but they can be a |

| |little more complex to work with. A three dimensional chart can |

| |be rotated so that it can be seen from other perspectives. 3-D |

| |charts are often used for the added dramatic impact they provide |

| |to a presentation. |

|Think about an inquiry project that your students might engage in| |

|within your domain. When would you use this graph? What data | |

|would you need to have? | |

| | |

|Write 2 questions that you could ask your classmates to test if | |

|they understand what this graph means. | |

| | |

| | |

| | |

Surface graphs let you plot three dimensional data sets and functions. On a surface plot, the X and Y values determine the reference coordinates for the Z values. NExS surface graphs are presented with perspective and shading. The shading can be either that of the surface when illuminated by light from a single point, or it can provide a color shading based on a Z value relative to the maximum and minimum Z values.

   [pic]

A contour graph is a two-dimensional representation of a surface graph. This graph type is analogous to maps showing elevation. Just as you set the number of histogram bins, you can set the number of contour levels. This is done with the Z-Axis Options dialog box. Disable Auto Ticks and place the desired number of contour levels in the Major entry box.

   [pic]

Polar graphs provide graphs of a data with respect to a polar coordinate system rather than a cartesian or rectangular coordinate system. A polar graph plots a point at some radial distance along a ray that creates a given angle with the positive X axis. For polar graphs, the angular measurement and radial components correspond to the X and Y coordinates in a line graph, respectively.

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