Difference between 0 and NaN in density/speed profiles

[schroedtert]

When computing the profiles there is currently no distinction between 0 and NaN values. When an cell is unoccupied it gets the value zero, which is the same for a cell with a standing pedestrian (speed = 0).

Is this the desired behavior or should unoccupied cells get NaN as a result?

[schroedtert]

After discussion:

• for density the value 0 has the meaning that there is no pedestrian in that area, hence the value is kept
• for speed, when computing the classic mean speed profile the fill value can now be set by the user. See documentation.