Display major and minor tick marks for log-scale axis

Display major and minor tick marks for log-scale axis, with optional offset for proper labeling of log2(1+x) with numeric offset.

minorLogTicksAxis(
  side = NULL,
  lims = NULL,
  logBase = 2,
  displayBase = 10,
  offset = 0,
  symmetricZero = (offset > 0),
  majorCex = 1,
  minorCex = 0.65,
  doMajor = TRUE,
  doLabels = TRUE,
  doMinorLabels = TRUE,
  asValues = TRUE,
  padj = NULL,
  doFormat = TRUE,
  big.mark = ",",
  scipen = 10,
  minorWhich = c(2, 5),
  logStep = 1,
  cex = 1,
  las = 2,
  col = "black",
  col.ticks = col,
  minorLogTicksData = NULL,
  verbose = FALSE,
  ...
)

Arguments

side: integer indicating the axis side, 1=bottom, 2=left, 3=top, 4=right.
lims: NULL or numeric range for which the axis tick marks will be determined. If NULL then the corresponding par("usr") will be used.
logBase: numeric value indicating the log base units, which will be used similar to how base is used in log(x, base).
displayBase: numeric value indicating the log base units to use when determining the numeric label position. For example, data may be log2 scaled, and yet it is visually intuitive to show log transformed axis units in base 10 units. See examples.
offset: numeric offset used in transforming the numeric data displayed on this axis. For example, a common technique is to transform data using log2(1+x) which adds 1 to values prior to the log2 transformation. In this case, offset=1, which ensures the axis labels exactly match the initial numeric value prior to the log2 transform.
symmetricZero: logical indicating whether numeric values are symmetric around zero. For example, log fold changes should use symmetricZero=TRUE which ensures a log2 value of -2 is labeled -4 to indicate a negative four fold change. If symmetricZero=FALSE a log2 value of -2 would be labeled 0.0625.
majorCex, minorCex: the base text size factors, relative to cex=1 for default text size. These factors are applied in addition to existing par("cex") values, preserving any global text size defined there.
padj: numeric vector length 2, which is used to position axis labels for the minor and major labels, respectively. For example, padj=c(0,1) will position minor labels just to the left of the tick marks, and major labels just to the right of tick marks. This example is helpful when minor labels bunch up on the right side of each section.
doFormat: logical indicating whether to apply base::format() to format numeric labels.
big.mark, scipen: parameters passed to base::format() when doFormat=TRUE.
minorWhich: integer vector indicating which of the minor tick marks should be labeled. Labels are generally numbered from 2 to displayBase-1. So by default, log 10 units would add minor tick marks and labels to the c(2,5) position. For log2 units only, the second label is defined at 1.5, which shows minor labels at c(3, 6, 12), which are 1.5 * c(2, 4, 8).
cex, col, col.ticks, las: parameters used for axis label size, axis label colors, axis tick mark colors, and label text orientation, respectively.
minorLogTicksData: a list object created by running jamba::minorLogTicks(), which allows inspecting and modifying the content for custom control.
verbose: logical indicating whether to print verbose output.

Value

list with vectors:

majorLabels: character vector of major axis labels
majorTicks: numeric vector of major axis tick positions
minorLabels: character vector of minor axis labels
minorTicks: numeric vector of minor axis tick positions
allLabelsDF: data.frame containing all axis tick positions and corresponding labels.

Details

This function displays log units on the axis of an existing base R plot. It calls jamba::minorLogTicks() which calculates appropriate tick and label positions.

Note: This function assumes the axis values have already been log-transformed. Make sure to adjust the offset to reflect the method of log-transformation, for example:

log2(1+x) would require logBase=2 and offset=1 in order to represent values properly at or near zero.
log(0.5+x) would require logBase=exp(1) and offset=0.5.
log10(x) would require logBase=10 and offset=0.

The defaults logBase=2 and displayBase=10 assume data has been log2-transformed, and displays tick marks using the common base of 10. To display tick marks at two-fold intervals, use displayBase=2.

This function was motivated in order to label log-transformed data properly in some special cases, like using log2(1+x) where the resulting values are shifted "off by one" using standard log-scaled axis tick marks and labels.

For log fold changes, set symmetricZero=TRUE, which will create negative log scaled fold change values as needed for negative values. For example, this option would label a logBase=2 value of -2 as -4 and not as 0.25.

Note that by default, whenever offset > 0 the argument symmetricZero=TRUE is also defined, since a negative value in that scenario has little meaning. This behavior can be turned off by setting symmetricZero=FALSE.

Examples

plotPolygonDensity(0:100, breaks=100);


plotPolygonDensity(0:100, breaks=100, log="x",
   main="plotPolygonDensity() uses minorLogTicksAxis()",
   xlab="x (log-scaled)");


plotPolygonDensity(log2(1+0:100), breaks=100,
   main="manually called minorLogTicksAxis(logBase=2)",
   xaxt="n",
   xlab="x (log-scaled)");
minorLogTicksAxis(1, offset=1, logBase=2);


plotPolygonDensity(log10(1+0:100), breaks=100,
   main="manually called minorLogTicksAxis(logBase=10)",
   xaxt="n",
   xlab="x (log-scaled)");
minorLogTicksAxis(1, offset=1, logBase=10);


plotPolygonDensity(log10(1+0:100), breaks=100,
   main="using 'minorWhich=2:9'",
   xaxt="n",
   xlab="x (log-scaled)");
minorLogTicksAxis(1, offset=1, logBase=10,
   minorWhich=2:9);

Display major and minor tick marks for log-scale axis

Arguments

Value

Details

See also

Examples