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WLDiagram

R class WLDiagram draws a Walter and Lieth (1960) diagram.

WLDiagram R class

The R class WLDiagram draws a Walter and Lieth (1960) diagram. Units for the diagram can be either SI or Imperial.

This class was originally part of the R package ClimatePrimers, produced at the Natural Resource Ecology Laboratory, Colorado State University, and previously at the North Central Climate Adaptation Science Center at Colorado State University.

Usage

Package ‘grid’ draws the plot. A grob (grid plot object) is returned, which can then be displayed with ‘grid.draw’.

Climatic data is a data.frame containing 12 columns (one per month, January to December) and 4 rows, one per variable. The variables are:

variable	description	units
prec	Mean monthly precipitation	in or mm
tmin	Mean maximum daily temperature per month	F or C
tmax	Mean minimum daily temperature per month	F or C
atmn	Absolute monthly minimum temperature per month	F or C

Absolute monthly minimum temperature is used to determine the probable frost months (when absolute monthly minimums are equal or lower than 0 C).

As described by Walter and Lieth, when monthly precipitation is greater than 100 mm, the scale is increased from 2 mm/C to 20 mm/C to avoid too high diagrams in very wet locations. This change is indicated by a black horizontal line, and the graph over it is filled in solid blue.

When the precipitation graph lies under the temperature graph (P < 2T) we have an arid period (filled in dotted red vertical lines). Otherwise the period is considered wet (filled in blue lines), unless ‘p3line=TRUE’, that draws a precipitation black line with a scale P = 3T; in this case the period in which 3T > P > 2T is considered semi-arid.

Daily maximum average temperature of the hottest month and daily minimum average temperature of the coldest month are frequently used in vegetation studies, and are labeled in black at the left margin of the diagram.

About WLDiagram::diagwl.grid plot function

This function was modified the from the climatol::diagwl function; see the R package climatol for the original.

Modifications to the original function:

The original used the R base graphics package. This version uses the R grid package.
The original diagwl function returns the final grob. This version returns a grobTree.
Added English translations to the original Spanish comments.
Added additional error checks.
Added optional display of English units along with SI units.
Viewport is only in npc units; lines units are not used.
Code for drawing of the precipitation line with diagonal lines under it, has been rewritten.

Run the test

R  # start the R console in this directory
source( "Test_WLDiagram.R" )

Explaination of the diagram

The Walter and Lieth (1960, 1963) climate diagrams summarize mean precipitation and temperature for one site or region. Vertical scales are constant so that the visual pattern from different locations can be quickly compared. The astronomic summer is always shown in the middle of the diagram, hence the month scale begins in January in the northern hemisphere, and July in the southern. Vertical blue lines indicate humid periods, and dashed red lines indicate dryer periods. Months with likely frost and probable frost are shown in the bar at 0 C.

Author

Thomas E. Hilinski tom.hilinski@colostate.edu

Plot function is derived from function diagwl in the R package climatol, written by Jose A. Guijarro

Suggestions and feedback were provided by Dennis Ojima and Robert Flynn at the Natural Resource Ecology Laboratory, Colorado State University.

Files

WLDiagram.R            - class WLDiagram

ClimateVars.R          - Functions for climate variable names
MiscUtils.R            - Miscellaneous functions
TextProcessing.R       - Utilities for modifying text for display
Units.R                - Units conversion functions
PlotBase.R             - Base class for class WLDiagram

Test_WLDiagram.R       - Test class WLDiagram
data_PerMonth.rds      - Data for test
Example-WLDiagram.png  - Plot produced by test script.

Reference

Walter, H., Lieth, H., 1960. Klimadiagramma-Weltatlas. G. Fischer Verlag, Jena.

License

See the file LICENSE.md in this repository.