Check for consistency in attribute slots within “Stem” Objects

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Description

Stem class constructors allow one to specify both taper and total stem attributes such as volume and biomass. This function checks to make sure that any inconsistencies between the taper version of these attributes and those specified in the constructor are not too large. See below for details.

Usage

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checkStemDimensions(stem, tolerancePercent = 1, ...)

Arguments

stem

An object that is a subclass of "Stem"

tolerancePercent

The tolerance limit in percent (the default is 1 percent). Differences larger than this will result in a warning.

...

Just gobbled for now.

Details

If one specifies a volume (optional) for a “Stem” object in the constructor in addition to the taper data (required), the two may not necessarily be in agreement. The same is true for other attibutes like surface area, etc. This is okay for the usual Horvitz-Thompson type estimators where the sampling surface is flat (constant) within a given inclusion zone. The routines use the entered volume for estimation and the taper data for graphical display. However, the Monte Carlo sampling methods (such as distance limited sampling for down logs, or critical height sampling for standing trees) use the taper data to determine heights or diameters along the bole as part of the estimate. Thus, if the two values for volume (that in the volume slot and that given by integration of the taper data) are not closely commensurate, it can result in an unintended apparent bias in the simulations. Note also that methods like perpendicular distance sampling rely on the taper data for the inclusion zone, so there could be a bias produced here as well.

This function can be used to check how closely the slot and taper values correspond for a given “Stem” subclass object, and will print a warning if the discrepancy is too large. One should not ignore this warning in the cases mentioned above. More information on this is given in the reference below.

Value

A list is returned invisibly with...

stemID

The stem ID value.

tolerancePercent

The value of the above argument specified by the user.

volume

A vector with elements: 1. volume from the slot, 2. volume from either the taper function or Smalian's, depending on solidType, 3. splined volume from the taper data, 4. the percent difference.

surfaceArea

A vector with elements: 1. surface area slot, 2. splined or taper SA depending on solidType, 3. percent difference.

coverageArea

As above in surfaceArea but for coverage area.

biomass

A vector with elements: 1. biomass slot value, 2. conversion from volume[2], 3. percent difference. Note that if no biomass is specified in the respective object slot, all will be NA.

carbon

As above for biomass but for carbon.

Note

Note that as of sampSurf version 0.7-2 this function is run automatically within the constructors for down logs or standing trees. However, one can run it at any time as a check on the object, just like one can invoke validObject at any time.

Author(s)

Jeffrey H. Gove

References

Gove, J. H. 2014. Apparent bias in sampSurf. R sampSurf package vignette series paper.

See Also

"Stem", "downLog", "standingTree"

Examples

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## Not run: 
st = standingTree(dbh=20, height=20, solidType=3)
checkStemDimensions(st)
st2 = standingTree(dbh=20, height=20, solidType=3, treeVol=1.1*st@treeVol)
checkStemDimensions(st2)

## End(Not run)

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