Generates area estimates by domain (and estimation unit). Calculations are based on Scott et al. 2005 ('the green-book') for mapped forest inventory plots. The non-ratio estimator for estimating area by stratum and domain is used. Plots that are totally nonsampled are excluded from estimation dataset. Next, an adjustment factor is calculated by strata to adjust for nonsampled (nonresponse) conditions that have proportion less than 1. The attribute is the proportion of the plot which is divided by the adjustment factor, and averaged by stratum. Strata means are combined using the strata weights and then expanded to area using the total land area in the population.
modGBdwm(
GBpopdat = NULL,
dwmtype = "CWD",
dwmvar = "VOLCF",
peracre = FALSE,
lbs2tons = FALSE,
landarea = "FOREST",
pcfilter = NULL,
vfilter = NULL,
rowvar = NULL,
colvar = NULL,
sumunits = TRUE,
returntitle = FALSE,
savedata = FALSE,
table_opts = NULL,
title_opts = NULL,
savedata_opts = NULL,
gui = FALSE,
...
)List. Population data objects returned from modGBpop().
String. Type of dwm estimate ('CWD', 'FWD_LG', "FWD_MD", "FWD_SM").
String. Type of dwm estimate ('VOLCF', 'BIOMASS', "CARBON").
Logical. If TRUE, generates per-acre estimates.
Logical. If TRUE, converts biomass or carbon variables from pounds to tons. If metric=TRUE, converts to metric tons, else short tons.
String. The sample area filter for estimates ("ALL", "FOREST", "TIMBERLAND"). If landarea=FOREST, filtered to COND_STATUS_CD = 1; If landarea=TIMBERLAND, filtered to SITECLCD in(1:6) and RESERVCD = 0.
String. A filter for plot or cond attributes (including pltassgn). Must be R logical syntax.
String. A filter for the P2 vegetation table used for estimate. Must be R logical syntax.
String. Name of row domain variable in cond. If only one domain, rowvar = domain variable. If more than one domain, include colvar. If no domain, rowvar = NULL.
String. Name of column domain variable in cond.
Logical. If TRUE, estimation units are summed and returned in one table.
Logical. If TRUE, returns title(s) of the estimation table(s).
Logical. If TRUE, saves table(s) to outfolder.
List. See help(table_options()) for a list of options.
List. See help(title_options()) for a list of options.
List. See help(savedata_options()) for a list of options. Only used when savedata = TRUE.
Logical. If gui, user is prompted for parameters.
Parameters for modGBpop() if GBpopdat is NULL.
A list with estimates with percent sampling error for rowvar (and colvar). If sumunits=TRUE or unitvar=NULL and colvar=NULL, one data frame is returned. Otherwise, a list object is returned with the following information. If savedata=TRUE, all data frames are written to outfolder.
Data frame. Area estimates, in area units (e.g., acres), by rowvar, colvar (and estimation unit). If sumunits=TRUE or one estimation unit and colvar=NULL, or allin1=TRUE, estimates and percent sampling error are in one data frame.
Data frame. Percent sampling errors (Confidence level 68 unit).
List. If returntitle=TRUE a list with table title(s). The list contains one title if est and pse are in the same table and two titles if est and pse are in separate tables. Row and column tables are also included in list.
List. If rawdata=TRUE, a list including the processing data used for estimation including: number of plots and conditions; stratification information; and 1 to 8 tables with calculated values for table cells and totals (See processing data below).
Raw data
Table. Number of plots by plot status (e.g., sampled forest on plot, sampled nonforest, nonsampled).
DF. Number of conditions by condition status (forest land, nonforest land, noncensus water, census water, nonsampled).
DF. Area by estimation unit.
DF. Condition-level area expansion factors.
DF. Final data table used for estimation.
Data frame. Strata information by estimation unit.
| Variable | Description | |
| unitvar | estimation unit | |
| strvar | stratum value | |
| strwtvar | number of pixels by strata and estimation unit | |
| n.strata | number of plots in strata (after totally nonsampled plots removed) | |
| n.total | number of plots for estimation unit | |
| strwt | proportion of area (or plots) by strata and estimation unit (strata weight) | |
| CONDPROP_UNADJ_SUM | summed condition proportion by strata and estimation unit | |
| CONDPROP_ADJFAC | adjusted condition proportion by strata after nonresponse plots removed | |
| AREA | total area for estimation unit | |
| CONDPROP_ADJFAC | average area |
Data frames. Separate data frames containing calculated variables used in estimation process. The number of processing tables depends on the input parameters. The tables include: total by estimation unit (unit.totest); rowvar totals (unit.rowest), colvar totals, if not NULL (unit.colvar); and a combination of rowvar and colvar, if colvar is not NULL (unit.grpvar). If sumunits=TRUE, the raw data for the summed estimation units are also included (totest, rowest, colest, grpest, respectively). These tables do not included estimate proportions (nhat and nhat.var).
The data frames include the following information:
| Variable | Description | |
| nhat | estimate proportion of land | |
| nhat.var | variance estimate of estimated proportion of land | |
| NBRPLT.gt0 | Number of non-zero plots used in estimates | |
| AREA | total area for estimation unit | |
| est | estimated area of land nhat*areavar | |
| est.var | variance estimate of estimate acres of land nhat.var*areavar^2 | |
| est.se | standard error of estimated area of land sqrt(est.var) | |
| est.cv | coefficient of variation of estimated area of land est.se/est | |
| pse | percent sampling error of estimate est.cv*100 | |
| CI99left | left tail of 99 percent confidence interval for estimated area | |
| CI99right | right tail of 99 percent confidence interval for estimated area | |
| CI95left | left tail of 95 percent confidence interval for estimated area | |
| CI95right | right tail of 95 percent confidence interval for estimated area | |
| CI67left | left tail of 67 percent confidence interval for estimated area | |
| CI67right | right tail of 67 percent confidence interval for estimated area |
savedata
if savedata=TRUE...
tables with estimate and percent standard
error will be written as *csv files to outfolder. if rawdata=TRUE, the
rawdata will be output to the outfolder in a folder named rawdata (if
raw_fmt="csv") or a database in the outfolder, if (raw_fmt != "csv").
if outfn.pre is not null...
a prefix is added to output files if raw_fmt
= 'csv', prefix is added to file names in rawdata folder if raw_fmt !=
'csv', prefix is added to dsn name
If variables are NULL, then it will prompt user to input variables.
Necessary variables:
| Data | Variable | Description | |
| cond | cuniqueid | Unique identifier for each plot, to link to pltassgn (ex. PLT_CN). | |
| CONDID | Unique identifier of each condition on plot. Set CONDID=1, if only 1 condition per plot. | ||
| CONDPROP_UNADJ | Unadjusted proportion of condition on each plot. Set CONDPROP_UNADJ=1, if only 1 condition per plot. | ||
| COND_STATUS_CD | Status of each forested condition on plot (i.e. accessible forest, nonforest, water, etc.) | ||
| NF_COND_STATUS_CD | If ACI=TRUE. Status of each nonforest condition on plot (i.e. accessible nonforest, nonsampled nonforest) | ||
| SITECLCD | If landarea=TIMBERLAND. Measure of site productivity. | ||
| RESERVCD | If landarea=TIMBERLAND. Reserved status. | ||
| pltassgn | puniqueid | Unique identifier for each plot, to link to cond (ex. CN). | |
| STATECD | Identifies state each plot is located in. | ||
| INVYR | Identifies inventory year of each plot. | ||
| PLOT_STATUS_CD | Status of each plot (i.e. sampled, nonsampled). If not included, all plots are assumed as sampled. |
For available reference tables: sort(unique(FIESTAutils::ref_codes$VARIABLE))
ADJUSTMENT FACTOR:
The adjustment factor is necessary to account for
nonsampled conditions. It is calculated for each estimation unit by strata
by summing the unadjusted condition proportions (CONDPROP_UNADJ) and
dividing by the number of plots in the strata/estimation unit.
If ACI=FALSE, only nonsampled forest conditions are accounted for in the
adjustment factor.
If ACI=TRUE, the nonsampled nonforest conditions are
removed as well and accounted for in adjustment factor. This is if you are
interested in estimates for all lands or nonforest lands in the
All-Condition-Inventory.
STRATA:
Stratification is used to reduce variance in population estimates
by partitioning the population into homogenous classes (strata), such as
forest and nonforest. For stratified sampling methods, the strata sizes
(weights) must be either known or estimated. Remotely-sensed data is often
used to generate strata weights with proporation of pixels by strata. If
stratification is desired (strata=TRUE), the required data include: stratum
assignment for the center location of each plot, stored in either pltassgn
or cond; and a look-up table with the area or proportion of the total area
of each strata value by estimation unit, making sure the name of the strata
(and estimation unit) variable and values match the plot assignment name(s)
and value(s).
sumunits:
An estimation unit is a population, or area of interest, with
known area and number of plots. Individual counties or combined
Super-counties are common estimation units for FIA. An estimation unit may
also be a subpopulation of a larger population (e.g., Counties within a
State). Subpopulations are mutually exclusive and independent within a
population, therefore estimated totals and variances are additive. For
example, State-level estimates are generated by summing estimates from all
subpopulations within the State (Bechtold and Patterson. 2005. Chapter 2).
Each plot must be assigned to only one estimation unit.
If sumunits=TRUE, estimates are generated by estimation unit, summed together, and returned as one estimate. If rawdata=TRUE, estimates by individual estimation unit are also returned.
If sumunits=FALSE, estimates are generated and returned by estimation unit as one data frame. If savedata=TRUE, a separate file is written for each estimation unit.
stratcombine:
If TRUE and less than 2 plots in any one estimation unit,
all estimation units with 10 or less plots are combined. The current method
for combining is to group the estimation unit with less than 10 plots with
the estimation unit following in consecutive order (numeric or
alphabetical), restrained by survey unit (UNITCD) if included in dataset,
and continuing until the number of plots equals 10. If there are no
estimation units following in order, it is combined with the estimation unit
previous in order.
rowlut/collut:
There are several objectives for including rowlut/collut
look-up tables: 1) to include descriptive names that match row/column codes
in the input table; 2) to use number codes that match row/column names in
the input table for ordering rows; 3) to add rows and/or columns with 0
values for consistency. No duplicate names are allowed.
Include 2 columns in the table:
1-the merging variable with same name as
the variable in the input merge table;
2-the ordering or descriptive
variable.
If the ordering variable is the rowvar/colvar in the input
table and the descriptive variable is in rowlut/collut, set
row.orderby/col.orderby equal to rowvar/colvar. If the descriptive variable
is the rowvar/colvar in the input table, and the ordering code variable is
in rowlut/collut, set row.orderby/col.orderby equal to the variable name of
the code variable in rowlut/collut.
Scott, Charles T.; Bechtold, William A.; Reams, Gregory A.; Smith, William D.; Westfall, James A.; Hansen, Mark H.; Moisen, Gretchen G. 2005. Sample-based estimators used by the Forest Inventory and Analysis national information management system. Gen. Tech. Rep. SRS-80. Asheville, NC: U.S. Department of Agriculture, Forest Service, Southern Research Station, p.53-77.