Trendlines are horizontal or vertical reference lines, which help viewers easily interpret data. You can use them to set the context for data (with tooltips) or define limits and targets.
There are various ways to customize trendlines in your charts and widgets:
Trendlines in Charts
You can insert a trendline in a chart, to attract the attention of viewers to a particular section within data values, on any of the axes. You can use attributes to customize the color, thickness, and transparency of a trendline.
Let us suppose you are plotting the yearly revenues earned by a company over the last 10 years. The X-axis has the years marked, while the Y-axis has the revenues plotted. If you calculate the average of yearly revenues and insert a trendline at that position on the Y-axis, viewers will be able to quickly see which years were more successful for the company. You can also calculate the yearly growth rate of revenue and insert a second trendline in the chart. If you provide radio buttons for both trendlines at the bottom of the chart (as in the sample), viewers will be able to switch between the trendlines at will, depending on what they want to analyze.
Trendlines in Gauges
You can insert a trendline in a gauge, to draw the attention of visitors to values that provide additional context about the data. You can use attributes to customize the color, thickness, and transparency of a trendline.
Let us suppose you are plotting the CPU utilization of a particular computer in an angular gauge, where you have ranges for “low”, “medium”, and “high”. Within the range marked “high”, you can mark a point, at which the stress on CPU must be reduced, to prevent damage. You can insert a trendline at this point to help users quickly identify it.
Trend zones are similar to trend lines, except that they mark out an entire range of values, rather than just a single value. You can insert a trendzone in a chart or gauge by setting its starting point and end point. You can also use attributes to customize the color, thickness, and transparency of the trendzone. You can also add a tooltip to a trendzone to add more content to the range of values it covers.
Let us suppose you plot the number of trains carrying passengers into various cities from outside, in a bar chart. You can add a trendzone to mark the zone between the minimum and maximum numbers of passengers that the available trains can support. If the number is lower than the minimum, then viewers would understand that too few people are using the trains. On the contrary, if the number is higher than the maximum limit, then it will be easy to understand that the trains are overcrowded.
Vertical lines are elements that can help viewers differentiate between data blocks in a chart. You can place them between any two data points, or align them to specific data points.
Let us suppose you are plotting the monthly assets and liabilities of a bank in a multi-series line chart. You might want to insert a vertical line in the chart, at the point of ending of the financial year. That way, the viewers will be able to quickly understand how successful the beginning of the new financial year has been.
You can use a regression line to show the trend of y values for the x values or the trend of x values for the y values. A regression line is rendered as a straight line. You can, therefore, use it to derive a particular trend from the scattered data points in the chart canvas and predict values accordingly.
Let us suppose you are plotting the distance traveled by passengers on trains owned by a particular organization, in a scatter chart. You can insert a regression line within the chart to indicate how the percentage of passengers on board the trains reduces with distance. If you indicate percentage of passengers with X and distance travelled with Y, then you can display the chart in two forms. One is to represent X as a function of Y (X on Y) and the other is to represent Y as a function of X (Y on X). You can provide two radio buttons below the chart that the viewer can click to switch between the two types on the fly.