granstat {G2Sd}

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, web_interface=FALSE, statistic = "all", aggr = TRUE, modes = FALSE)

Arguments

x

A numeric matrix or data frame

web_interface

if TRUE, a simplified interface is displayed from your default web browser

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

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.

Value

A matrix containing

mean.arith

the mean of grain-size distribution (arithmetic method of moments)

sd.arith

the standard-deviation of grain-size distribution (arithmetic method of moments)

skewness.arith

the skewness of grain-size distribution (arithmetic method of moments)

kurtosis.arith

the kurtosis of grain-size distribution (arithmetic method of moments)

mean.geom

the mean of grain-size distribution (geometric method of moments

sd.geom

the standard-deviation of grain-size distribution (geometric method of moments)

skewness.geom

the skewness of grain-size distribution (geometric method of moments)

kurtosis.geom

the kurtosis of grain-size distribution (geometric method of moments)

Sediment

physical description of the sediment, the sorting, the skewness and the kurtosis

Mean.fw.mm

the mean of grain-size distribution (logarithmic Folk and Ward method, mm scale)

Sd.fw.mm

the standard-deviation of grain-size distribution (logarithmic Folk and Ward method, mm scale)

Skewness.fw.mm

the skewness of grain-size distribution (logarithmic Folk and Ward method, mm scale)

Kurtosis.fw.mm

the kurtosis of grain-size distribution (logarithmic Folk and Ward method, mm scale)

Mean.fw.phi

the mean of grain-size distribution (logarithmic Folk and Ward method, phi scale)

Sd.fw.phi

the standard-deviation of grain-size distribution (logarithmic Folk and Ward method, phi scale)

Skewness.fw.phi

the skewness of grain-size distribution (logarithmic Folk and Ward method, phi scale)

Kurtosis.fw.phi

the kurtosis of grain-size distribution (logarithmic Folk and Ward method, phi scale)

Mode

the mode (mm scale), graphically defined by the user

D10(mm)

the 10th percentile

D50(mm)

the median

D90(mm)

the 90th percentile

D90/D10

ratio of the 90th percentile and the 10th percentile

D90-D10

difference between the the 90th percentile and the 10th percentile

D75/D25

ratio of the 75th percentile and the 25th percentile

D75-D25

difference 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)

Texture

physical description of the texture of the sediment

Boulder

percentage of sediment of the grain-size distribution retained in the Boulder class (upper to 63 mm)

Gravel

percentage of sediment of the grain-size distribution retained in the Gravel class (between 2 mm and 63 mm)

Sand

percentage of sediment of the grain-size distribution retained in the Sand class (between 63 micrometer and 2 mm)

Mud

percentage of sediment of the grain-size distribution retained in the Mud class (down to 63 micrometer)

Boulder

percentage of sediment of the grain-size distribution retained in the Boulder class (upper to 63 mm)

vcgravel

percentage of sediment of the grain-size distribution retained in the Very Coarse Gravel class (between 31.5 mm and 63 mm)

cgravel

percentage of sediment of the grain-size distribution retained in the Coarse Gravel class (between 16 mm and 31.5 mm)

mgravel

percentage of sediment of the grain-size distribution retained in the Medium Gravel class (between 8 mm and 16 mm)

fgravel

percentage of sediment of the grain-size distribution retained in the Fine Gravel class (between 4 mm and 8 mm)

vfgravel

percentage of sediment of the grain-size distribution retained in the Very Fine Gravel class (between 2 mm and 4 mm)

vcsand

percentage of sediment of the grain-size distribution retained in the Very Coarse Sand class (between 1 mm and 2 mm)

csand

percentage of sediment of the grain-size distribution retained in the Coarse Sand class (between 500 micrometer and 1 mm)

msand

percentage of sediment of the grain-size distribution retained in the Medium Sand class (between 250 micrometer and 500 micrometer)

fsand

percentage of sediment of the grain-size distribution retained in the Fine Sand class (between 125 micrometer and 250 micrometer)

vfsand

percentage of sediment of the grain-size distribution retained in the Very Fine Sand class (between 63 micrometer and 125 micrometer)

vcsilt

percentage of sediment of the grain-size distribution retained in the Very Coarse Silt class (between 40 micrometer and 63 micrometer)

silt

percentage of sediment of the grain-size distribution retained in the Silt class (lower than 40 micrometer)

Author(s)

Regis K. Gallon (MNHN) [e-mail], Jerome Fournier (CNRS) [e-mail]

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

#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)

#to display the simplified interface
#granstat(web_interface=TRUE)