JSS 3 - CHARTS AND GRAPHS

CHART AND GRAPHS

A graph is a representation of a set of objects where some pairs of the objects are connected by lines. Or graph is a diagram that shows relationship between numbers or figures. The quantities are usually measured along two axes( x and y). A graph is also called chart.

While a chart is a graphical representation of data, in which "the data is represented by symbols, such as bars in a bar chart, lines in a line chart, or slices in a pie chart". A chart can represent tabular numeric data, functions or some kinds of qualitative structure and provides different info.

Charts are often used to ease understanding of large quantities of data and the relationships between parts of the data. Charts can usually be read more quickly than the raw data. They are used in a wide variety of fields, and can be created by hand (often on graph paper) or by computer using a charting application. Certain types of charts are more useful for presenting a given data set than others.

 

Some of the uses of graph

1.       To display results of computer mathematical solutions in diagrammatic forms

2.       To indicate the relationship between two or more variable quantities.

3.       It helps in enhancing report presentation.

4.       It helps in comparing variables in a table.

Features of a chart

A chart can take a large variety of forms, however there are common features that provide the chart with its ability to extract meaning from data.

a.       Typically the data in a chart is represented graphically, since humans are generally able to infer meaning from pictures quicker than from text. Text is generally used only to annotate the data.

b.      One of the most important uses of text in a graph is the title. A graph's title usually appears above the main graphic and provides a succinct description of what the data in the graph refers to.

c.       Dimensions in the data are often displayed on axes. If a horizontal and a vertical axis are used, they are usually referred to as the x-axis and y-axis respectively.

d.      Within the graph a grid of lines may appear to aid in the visual alignment of data. The grid can be enhanced by visually emphasizing the lines at regular or significant graduations.

e.      The data of a chart can appear in all manner of formats, and may include individual textual labels describing the datum associated with the indicated position in the chart. The data may appear as dots or shapes, connected or unconnected, and in any combination of colors and patterns. Inferences or points of interest can be overlaid directly on the graph to further aid information extraction.

Examples of common graphs/charts

Four of the most common charts are:

·         A histogram consists of tabular frequencies, shown as adjacent rectangles, erected over discrete intervals (bins), with an area equal to the frequency of the observations in the interval; first introduced by Karl Pearson.

 

DIAGRAM OF A HISTOGRAM CHART

 

·         A bar chart is a chart with rectangular bars with lengths proportional to the values that they represent. The bars can be plotted vertically or horizontally. The first known bar charts are usually attributed to Nicole Oresme, Joseph Priestley, and William Playfair.

MARKETING AND PROMOTION EXPENSES GRAPH

 

·         A pie chart shows percentage values as a slice of a pie; first introduced by William Playfair.

DIAGRAM OF A PIE CHART

·         A line chart is a two-dimensional scatterplot of ordered observations where the observations are connected following their order. The first known line charts are usually credited to Francis Hauksbee, Nicolaus Samuel Cruquius, Johann Heinrich Lambert and William Playfair.

DIAGRAM OF A LINE CHART

Other common charts are:

·         Timeline chart

·         Organizational chart

·         Tree chart

·         Flow chart

·         Area chart

·         Cartogram

·         Pedigree chart

Less-common charts

Examples of less common charts are:

·         Bubble chart

·         Polar area diagram

·         Waterfall chart

·         Radar chart

·         Tree map

·         Streamgraph

·         GapChart