## Bug report #22038

### Inconsistent intervals for similar labels in graduated classification

Status: | Open | ||
---|---|---|---|

Priority: | Normal | ||

Assignee: | - | ||

Category: | Symbology | ||

Affected QGIS version: | 3.4.6 | Regression?: | No |

Operating System: | Easy fix?: | No | |

Pull Request or Patch supplied: | No | Resolution: | |

Crashes QGIS or corrupts data: | No | Copied to github as #: | 29852 |

**Description**

Hi

There is currently an inconsistent meaning behind a similar appearance when we make a graduated classification.

In the legend label ... meaning we see for QGIS ------ ----------- a - b a ≤ x ≤ b b - c b < x ≤ c c - d c < x ≤ d

Note that the first class has left inclusion but not the others.

We could wrongly expect from reading only the label :

a - b equals to a ≤ x < b b - c equals to b ≤ x < c c - d equals to c ≤ x < d

... or any other scheme actually.

**So the same "class interval label" have different interpretations if they are the first or not**.

We need a label notation where the endpoints inclusions are explicit, for example :

common French style style ------- ------- [a, b] [a, b] (b, c] ]b, c] (c, d] ]c, d]

... or at least if we keep the basic "a - b" notation then we must use the same interval scheme for all classes.

Note also that some softwares (R for example) use left-open/right-closed intervals by default :

label -------------- meaning ------ ------ --------- (a, b] ]a, b] a < x ≤ b (b, c] ]b, c] b < x ≤ c (c, d] ]c, d] c < x ≤ d

... and some others (like openJUMP) are left-closed/right-open :

label -------------- meaning ------ ------ --------- [a, b) [a, b[ a ≤ x < b [b, c) [b, c[ b ≤ x < c [c, d) [c, d[ c ≤ x < dSo we need :

- to use a consistent scheme for all classes
- to add an option to be able to choose the left-open or right-open scheme
- to add an option to generate the label with the common notation, the French (Bourbaki) notation or any other notation.

Thanks