Description Usage Arguments Details Value Examples

Compute the moment of gravity force Mf and the moment of gravity force relative to cylinder radius Mf_r from an object of class aRchi.

1 2 3 4 | ```
Compute_Mf(aRchi, WoodDensity)
## S4 method for signature 'aRchi'
Compute_Mf(aRchi, WoodDensity = NULL)
``` |

`aRchi` |
an object of class aRchi with at least the QSM and the paths table. |

`WoodDensity` |
a numeric or a data.table. A single wood density value for the whole tree or one value per cylinder in kg/m3. If wood density is given for each cylinder a data.table with two column (i.e cyl_ID and WoodDensity) must be given. |

The moment of gravity force (i.e `Mf`

) is calculated at each cylinder position. `Mf`

can be seen as a proxy of the mechanical loading history due to gravity at a given position of a tree.
This quantity is defined by the following the equation: Mf=R*FALSE where R is the lever arm, which is the norm of the horizontal vector between the position where `Mf`

is measured (i.e a cylinder) and the position where the force is applied (i.e., the center of mass, G, of the whole structure upstream a cylinder: a subtree).

The mass of the cylinders are needed to calculate the center of mass and are estimated using their volume and the wood density provided in argument `WoodDensity`

. Finally, FALSE is the weight of the subtree: FALSE=g*M with g the standard acceleration due to gravity (9.81 m.s-²).

The moment of gravity force relative (i.e `Mf_r`

) to cylinder radius r is also computed following the formula: Mf_r = Mf/r^3

The aRchi file with the QSM slot having three new columns: the biomass upstream the cylinder `sub_tree_biomass`

, the moment of gravity force `Mf`

and the moment of gravity force relative to cylinder radius `Mf_r`

.

1 2 3 4 5 6 7 8 9 | ```
# Read an aRchi file with a QSM and paths tables.
file=system.file("extdata","Tree_1_aRchi.aRchi",package = "aRchi")
Tree1_aRchi=read_aRchi(file)
# Compute the moment of force for each cylinder
Tree1_aRchi=Compute_Mf(Tree1_aRchi,WoodDensity=550)
# show the QSM data.table with the three new columns sub_tree_biomass, MF and Mf_r)
get_QSM(Tree1_aRchi)
``` |

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