granstat: Calculates all descriptive statistics

Description

Statistics are calculated using arithmetic and geometric Method of Moments (micrometer) and using logarithmic Folk and Ward (1957) Method (phi scale): mean, standard-deviation, skewness, kurtosis. The mode(s) is(are) determined graphically by the user (with a maximum of 4 modes). The determination of the mode is optional (no determination by default). Several percentiles and common index are calculated: D10, D50, D90, D90/D10, D90-D10, D75/D25, D75-D25, Trask(So) Index, Krumbein(Qd) Index. Physical description of texture, sorting, skewness or kurtosis are provided as such as the sediment name after Folk (1954). Are also included the percentage of particules falling into each predefined size fraction, modified from Blott and Pye (2001) scale, Udden (1914) and Wentworth (1922). granstat is a function which provides all results organized in two ways: a complete matrix (by default) or by separate items.

Usage

granstat(x, statistic = "all", aggr = TRUE, modes = FALSE)

Arguments

A numeric matrix or data frame

statistic

Statistic used: "arithmetic", "geometric", "folk.ward", "all". If this argument is not used, all statistics are calculated

aggr

If TRUE, a complete matrix is provided. If FALSE, the results are organized in separate items: $stat, $index, $mode, $sedim. If this argument is not used, a complete matrix is provided

modes

If TRUE, the mode must be determinated graphically by the user. If FALSE, the mode is not determinated. If this argument is not used, no determination of the mode is proposed

Value

A matrix containing
mean.ariththe mean of grain-size distribution (arithmetic method of moments)
sd.ariththe standard-deviation of grain-size distribution (arithmetic method of moments)
skewness.ariththe skewness of grain-size distribution (arithmetic method of moments)
kurtosis.ariththe kurtosis of grain-size distribution (arithmetic method of moments)
mean.geomthe mean of grain-size distribution (geometric method of moments
sd.geomthe standard-deviation of grain-size distribution (geometric method of moments)
skewness.geomthe skewness of grain-size distribution (geometric method of moments)
kurtosis.geomthe kurtosis of grain-size distribution (geometric method of moments)
Sedimentphysical description of the sediment, the sorting, the skewness and the kurtosis
Mean.fw.mmthe mean of grain-size distribution (logarithmic Folk and Ward method, mm scale)
Sd.fw.mmthe standard-deviation of grain-size distribution (logarithmic Folk and Ward method, mm scale)
Skewness.fw.mmthe skewness of grain-size distribution (logarithmic Folk and Ward method, mm scale)
Kurtosis.fw.mmthe kurtosis of grain-size distribution (logarithmic Folk and Ward method, mm scale)
Mean.fw.phithe mean of grain-size distribution (logarithmic Folk and Ward method, phi scale)
Sd.fw.phithe standard-deviation of grain-size distribution (logarithmic Folk and Ward method, phi scale)
Skewness.fw.phithe skewness of grain-size distribution (logarithmic Folk and Ward method, phi scale)
Kurtosis.fw.phithe kurtosis of grain-size distribution (logarithmic Folk and Ward method, phi scale)
Modethe mode (mm scale), graphically defined by the user
D10(mm)the 10th percentile
D50(mm)the median
D90(mm)the 90th percentile
D90/D10ratio of the 90th percentile and the 10th percentile
D90-D10difference between the the 90th percentile and the 10th percentile
D75/D25ratio of the 75th percentile and the 25th percentile
D75-D25difference between the the 75th percentile and the 25th percentile
Trask(So)the Trask Index (So) defined as D25/D75 (mm scale)
Krumbein(Qd)the Krumbein Index (Qd) defined as (D25-D75)/2 (phi scale)
Texturephysical description of the texture of the sediment
Boulderpercentage of sediment of the grain-size distribution retained in the Boulder class (upper to 63 mm)
Gravelpercentage of sediment of the grain-size distribution retained in the Gravel class (between 2 mm and 63 mm)
Sandpercentage of sediment of the grain-size distribution retained in the Sand class (between 63 micrometer and 2 mm)
Mudpercentage of sediment of the grain-size distribution retained in the Mud class (down to 63 micrometer)
Boulderpercentage of sediment of the grain-size distribution retained in the Mud class (upper to 63 mm)
vcgravelpercentage of sediment of the grain-size distribution retained in the Mud class (between 31.5 mm and 63 mm)
cgravelpercentage of sediment of the grain-size distribution retained in the Mud class (between 16 mm and 31.5 mm)
mgravelpercentage of sediment of the grain-size distribution retained in the Mud class (between 8 mm and 16 mm)
fgravelpercentage of sediment of the grain-size distribution retained in the Mud class (between 4 mm and 8 mm)
vfgravelpercentage of sediment of the grain-size distribution retained in the Mud class (between 2 mm and 4 mm)
vcsandpercentage of sediment of the grain-size distribution retained in the Mud class (between 1 mm and 2 mm)
csandpercentage of sediment of the grain-size distribution retained in the Mud class (between 500 micrometer and 1 mm)
msandpercentage of sediment of the grain-size distribution retained in the Mud class (between 250 micrometer and 500 micrometer)
fsandpercentage of sediment of the grain-size distribution retained in the Mud class (between 125 micrometer and 250 micrometer)
vfsandpercentage of sediment of the grain-size distribution retained in the Mud class (between 63 micrometer and 125 micrometer)
vcsiltpercentage of sediment of the grain-size distribution retained in the Mud class (between 40 micrometer and 63 micrometer)
siltpercentage of sediment of the grain-size distribution retained in the Mud class (lower than 40 micrometer)

encoding

UTF8

Details

For the determination of the mode (modes=TRUE). All the samples are successively shown with a graph. The user can choose graphically the mode (1 in 4 maximum) by a click on the graph. If 4 modes are chosen, the following graph appears automatically. If 1, 2 or 3 modes are chosen, the user has to use the function stop locator in the graphic window. If the weight of sediment retained on the broadest sieve exceeds 5 percent of the total mass of the sample, the Folk and Ward statistics cannot be computed.

References

Blott, S., Pye, K. 2001. Gradistat: grain size distribution and statistics package for the analysis of unconsolidated sediment. Earth, Surface Processes and Landforms 26, 1237�1248 Folk, R.L. 1954. The distinction between grain size and mineral composition in sedimentary-rock nomenclature. Journal of Geology 62, 344-359 Folk, R.L., Ward, W.C. 1957. Brazos River bar: a study in the significance of grain size parameters. Journal of Sedimentary Petrology 27, 3-26 Krumbein, W.C., Pettijohn, F.J. 1938. Manual of Sedimentary Petrography. Appleton-Century-Crofts, New-York Udden, J.A. 1914. Mechanical composition of clastic sediments. Bulletin of the Geological Society of America 25, 655-744 Wentworth, C.K. 1922. A scale of grade and class terms for clastic sediments. Journal of Geology 30, 377-392

Examples

Run this code

#granulo is the data set
data(granulo)
granstat(granulo)
granstat(granulo,statistic="all",aggr=TRUE,modes=FALSE)
granstat(granulo,statistic="folk.ward",aggr=FALSE,modes=TRUE)

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