When we make charts that contain multiple data series, it happens that the data in them varies greatly, in terms of value ranges, or they are set in different units of measure. Also, we will sometimes want to show different series by using different chart types. For this purpose, we choose whether the series is displayed on the primary or secondary axis, and which type of chart we want to use to display the data on it.
Sometimes the chart will show values that are not reliable. In that case, it would be good to emphasize to the observer that the error exists, and how its tolerance is. For this purpose, error lines are used that express a potential error, relative to the point or marker for the given data set. They can also be used to highlight some future trends, or to make assumptions about future value data.
Charts are often expected to present the current state and projection of future events. Nobody reliably knows what will happen in the future, but by approximating past data, it is possible to identify trends. Trend, by definition, represents the general direction of development or change. Excel sets trends and displays them using the trend line by application of various mathematical functions.
Each chart consists of more elements that determine its appearance. This is, first of all, the way data are shown within a group (Data Series) or a single series (Data Point). Depending on the type of data, different charts are being used: Column, Bar, Line, Surface, Pie … Accordingly, the elements of such charts are: title, legend, axes, background … By adding or removing elements we ‘re getting the more effective report.