During histogram input, the following rules are checked. Violated rules generate error messages.
Each step number should be one more than the previous step number (unless -T4 is on). For column values for each step, the value should be greater than or equal to the previous step’s column value.
The column values for the steps must increase monotonically.
The weight for each cell must be between 0.0 and 1.0.
The total of weights for a column must be close to 1.0.
The first cell represents null values and it must be present, even for columns that do not allow null values. There must be only one cell representing the null value.
Two adjacent cells cannot both use the < operator.