Previous()
You use the Previous() navigation method in an expression, when you want to reference the previous node within the same level of the hierarchy.
This is exemplified below.
In case the value preceding the current node is not available (such as the Q3, 2019 value above), the method looks for the very previous, not missing, value (in this case Q2, 2019).
This method is commonly used to calculate differences, for example changes in the current quarter over the previous quarter as illustrated above.
Example
The data table lists weekly measured weights for a newborn child, and the weights are shown in a bar chart.
Assume you are interested in the child's weekly growth. Then you can apply the following expression on the value axis:
The expression calculates the differences week by week, that is, the value of each bar is calculated by subtracting the value of the previous bar. The bar furthest to the left is dropped, because there is no previous value to reference.
The same example is used in the Next() topic. Depending on whether Next() or Previous() is used, the resulting bars are presented differently.