zoo Reference Card

Creation

• zoo(x, order.by): Creation of a "zoo" object from the observations x (a vector or a matrix) and an index order.by by which the observations are ordered.

  For computations on arbitrary index classes, methods to the following generic functions are assumed to work: combining c(), querying length length(), subsetting [, ordering ORDER() and value matching MATCH(). For pretty printing an as.character and/or index2char method might be helpful.

Creation of regular series

• zoo(x, order.by, freq): Works as above but creates a "zooreg" object which inherits from "zoo" if the frequency freq complies with the index order.by. An as.numeric method has to be available for the index class.
• zooreg(x, start, end, freq): Creates a "zooreg" series with a numeric index as above and has (almost) the same interface as ts(). |

Standard methods

• plot: Plotting. Alternatives: xyplot (lattice), autoplot (ggplot2), tinyplot.
• lines: Adding a "zoo" series to a plot.
• print: Printing.
• summary: Summarizing (column-wise).
• str: Displaying structure of "zoo" objects.
• head, tail: Head and tail of "zoo" objects.

Import/export

• read.zoo: Reads "zoo" objects from text files, e.g., in CSV format (comma-separated values).
• write.zoo: Writes "zoo" objects to text files such, e.g., in CSV format.

Coercion

• as.zoo: Coercion to "zoo" is available for objects of class "ts", "xts", "timeSeries", and many others.
• as.class.zoo: Coercion from "zoo" to other classes. Includes methods for class in "matrix", "vector", "data.frame", "list", "ts", "xts", "timeSeries", and several others.
• is.zoo: Querying wether an object is of class "zoo".

Merging and binding

• merge: Union, intersection, left join, right join along indexes.
• cbind: Column binding along the intersection of the index.
• c, rbind: Combining/row binding (indexes may not overlap).
• aggregate: Compute summary statistics along a coarser grid of indexes

Mathematical operations

• Ops: Group generic functions performed along the intersection of indexes.
• t: Transposing (coerces to "matrix" before).
• cumsum: Compute (columnwise) cumulative quantities: sums cumsum(), products cumprod(), maximum cummax(), minimum cummin().

Extracting and replacing data and index

• index, time: Extract the index of a series.
• index<-, time<-: Replace the index of a series.
• coredata, coredata<-: Extract and replace the data associated with a "zoo" object.
• lag: Lagged observations.
• diff: Arithmetic and geometric differences.
• start, end: Querying start and end of a series.
• window, window<-: Subsetting of "zoo" objects using their index.

NA handling

• na.omit: Omit NAs.
• na.contiguous: Compute longest sequence of non-NA observations.
• na.fill: Impute NAs by filling gaps with specific values.
• na.locf: Impute NAs by carrying forward the last observation.
• na.approx, na.spline: Impute NAs by interpolation.
• na.trim: Remove leading and/or trailing NAs.

Rolling analytics

• rollapply: Apply a function to rolling margin of an array.
• rollmean: More efficient functions for computing the rolling mean, median and maximum are rollmean(), rollmedian() and rollmax(), respectively.

Methods for regular series

• is.regular: Checks whether a series is weakly (or strictly if strict = TRUE) regular.
• frequency, deltat: Extracts the frequency or its reciprocal value respectively from a series, for "zoo" series the functions try to determine the regularity and frequency in a data-driven way.
• cycle: Gives the position in the cycle of a regular series.

Time classes for monthly and quarterly data

• yearmon: Time index class for monthly data.
• yearqtr: Time index class for quarterly data.