respR (version 2.3.3)

convert_MR: Convert between units of absolute, mass-specific, or area-specific metabolic rates

Description

Converts metabolic rates to a different unit. These can be absolute rates (i.e. whole chamber or whole specimen e.g. mg/h), mass-specific rates (i.e. normalised by specimen mass e.g. mg/h/kg), or area-specific rates (i.e. normalised by specimen surface area e.g. mg/h/cm2). Input rates can be a numeric value or vector, in which case the converted rates are output as a numeric of the same length in the new units. Alternatively, input can be an object of class convert_rate() or convert_rate.ft(), in which case a new convert_rate or convert_rate.ft object is returned with all rates in the $summary and other elements converted to the new units. This allows you to convert results of analyses to a different unit without having to repeat the entire analysis.

Usage

convert_MR(
  x,
  from = NULL,
  to = NULL,
  S = NULL,
  t = NULL,
  P = NULL,
  quiet = FALSE
)

Value

If the x input rates are a numeric value or vector, output is a numeric value or vector of the same length. If x is a convert_rate or convert_rate.ft object, output is a new convert_rate or convert_rate.ft object with all rates in the $summary table, $rate.output and $output.unit elements converted to the new units. This allows you to convert results of analyses to a different unit without having to repeat the entire analysis.

Arguments

x

numeric value or vector, or object of class convert_rate or convert_rate.ft. Contains the rate(s) to be converted.

from

string. The unit of the input metabolic rate(s). Should be in the correct order: Oxygen/Time, Oxygen/Time/Mass or Oxygen/Time/Area. If x is a convert_rate or convert_rate.ft object this is extracted automatically and any input specified via from is ignored.

to

string. The unit to convert the metabolic rate(s) to. Should be in the correct order: Oxygen/Time, Oxygen/Time/Mass or Oxygen/Time/Area. See unit_args().

S

numeric. Salinity (ppt). Defaults to NULL. Used in conversion of some oxygen units. Freshwater should be entered as S = 0. If x is a convert_rate or convert_rate.ft object this is extracted automatically if present and any other input ignored.

t

numeric. Temperature(°C). Defaults to NULL. Used in conversion of some oxygen units. If x is a convert_rate or convert_rate.ft object this is extracted automatically if present and any other input ignored.

P

numeric. Pressure (bar). Used in conversion of some oxygen units. Defaults to a standard value of 1.013253 bar. If x is a convert_rate or convert_rate.ft object this is extracted automatically if present and any other input ignored.

quiet

logical. Suppresses the summary of the converted rates printed to the console. Default is FALSE.

Details

Units

Units are specified using from and to. These should be in the sequence Oxygen-Time (e.g. "mg/h") for absolute rates, Oxygen-Time-Mass (e.g. "mg/h/kg") for mass-specific rates, and Oxygen-Time-Area (e.g. "mg/h/cm2") for surface area-specific rates. If x is a convert_rate or convert_rate.ft object the from unit is extracted automatically.

A fuzzy string matching algorithm is used to accept various unit formatting styles. For example, "mg/h", "mg/H", "mg hr-1", "milligram per hour" are all parsed the same. See unit_args() for details of accepted units and their formatting.

Note some units require salinity (S) and temperature (t) to perform the conversion. For freshwater experiments, salinity should be entered as zero (i.e. S = 0). These conversions also require the atmospheric pressure (P). If not entered the default value of 1.013253 bar (standard pressure at sea level) is used. If x is a convert_rate or convert_rate.ft object, S, t, and P are extracted automatically if they are present (they may not be if the original rate conversion did not require them). They are also saved to the $inputs element of the output object.

More details

For convert_rate or convert_rate.ft inputs the primary $rate.output element is converted to the new unit and the $output.unit also updated to this new unit. These columns are also updated in the $summary table, and in addition the rate.abs column and, if relevant, the rate.m.spec or rate.a.spec column. Note, the $call element is updated to the convert_MR call and the original call to convert_rate or convert_rate.ft replaced. The $inputs element will still contain the original inputs, with the output.unit updated to the new to unit. In addition S, t, and P are added if they weren't already present.

More

For additional help, documentation, vignettes, and more visit the respR website at https://januarharianto.github.io/respR/

Examples

# Convert a numeric absolute rate to a different unit
convert_MR(-0.09, from = 'mg/min', to = 'umol/hr')

# Convert a vector of absolute rates to a different unit
convert_MR(c(-0.090, -0.081, -0.098),
           from = 'mg/min', to = 'umol/hr')

# Convert to a unit which requires S, t, & P
convert_MR(-0.09, from = 'mg/min', to = 'ml/hour',
           S = 0, t = 20, P = 1.01)

# Convert mass-specific rates
convert_MR(-0.09, from = 'mg/min/g', to = 'ml/hour/kg',
           S = 0, t = 20, P = 1.01)

# Convert area-specific rates
convert_MR(-0.09, from = 'mg/min/mm2', to = 'ml/hour/cm2',
           S = 0, t = 20, P = 1.01)

# Convert from units largely only used in older papers.
# E.g. cubic cm (e.g. Tang 1933, Head 1962)
convert_MR(0.1, from = 'cc/hr/gm', to = 'mg/hr/g',
           S = 30, t = 20, P = 1.01)
convert_MR(0.6, from = 'cm3/hr', to = 'mg/hr',
           S = 28, t = 12, P = 1.01)
# uL (e.g. Zeuthen 1953, Newell & Northcroft 1967)
convert_MR(400, from = 'ul/hr', to = 'mg/hr',
           S = 30, t = 15, P = 1.01)
convert_MR(0.5, from = 'ul/hr/mg', to = 'mg/hr/g',
           S = 0, t = 20, P = 1.01)
# mm3 (e.g. Newell & Roy 1973)
convert_MR(1.5, from = 'mm3/hr', to = 'mg/hr',
           S = 30, t = 15, P = 1.01)

# Convert rates in a 'convert_rate' object. This avoids having to repeat
# an entire analysis to see the output in different units.

# Make a convert_rate object
cnv_rt.obj <- urchins.rd %>%
  auto_rate() %>%
  convert_rate(oxy.unit = "mg/L",
               time.unit = "min",
               output.unit = "mg/hr/kg",
               volume = 1,
               mass = 0.05)

# Now convert all results to "umol/min/g".
# The 'from' units are identified automatically from the object.
cnv_rt.obj.new <- convert_MR(cnv_rt.obj,
                             to = "umol/min/g")

# Compare the two:
summary(cnv_rt.obj)
summary(cnv_rt.obj.new)