MatchIt: plot.summary.matchit – R documentation

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plot.summary.matchit

Generate a Love Plot of Standardized Mean Differences

Description

Generates a Love plot, which is a dot plot with variable names on the y-axis and standardized mean differences on the x-axis. Each point represents the standardized mean difference of the corresponding covariate in the matched or unmatched sample. Love plots are a simple way to display covariate balance before and after matching. The plots are generated using dotchart and points.

Usage

## S3 method for class 'summary.matchit'
plot(x, abs = TRUE, var.order = "data",
       threshold = c(.1, .05), position = "bottomright", ...)

Arguments

`x`	a `summary.matchit` object; the output of a call to `summary.matchit`. The `standardize` argument must be set to `TRUE` (which is the default) in the call to `summary`.
`abs`	`logical`; whether the standardized mean differences should be displayed in absolute value (`TRUE`, default) or not `FALSE`.
`var.order`	how the variables should be ordered. Allowable options include `"data"`, ordering the variables as they appear in the `summary` output; `"unmatched"`, ordered the variables based on their standardized mean differences before matching; `"matched"`, ordered the variables based on their standardized mean differences after matching; and `"alphabetical"`, ordering the variables alphabetically. Default is `"data"`. Abbreviations allowed.
`threshold`	numeric values at which to place vertical lines indicating a balance threshold. These can make it easier to see for which variables balance has been achieved given a threshold. Multiple values can be supplied to add multiple lines. When `abs = FALSE`, the lines will be displayed on both sides of zero. The lines are drawn with `abline` with the linetype (`lty`) argument corresponding to the order of the entered variables (see options at `par`). The default is `c(.1, .05)` for a solid line (`lty = 1`) at .1 and a dashed line (`lty = 2`) at .05, indicating acceptable and good balance, respectively. Enter a value as `NA` to skip that value of `lty` (e.g., `c(NA, .05)` to have only a dashed vertical line at .05).
`position`	the position of the legend. Should be one of the allowed keyword options supplied to `x` in `legend` (e.g., `"right"`, `"bottomright"`, etc.). Default is `"bottomright"`. Set to `NULL` for no legend to be included. Note that the legend will cover up points if you are not careful; setting `var.order` appropriately can help in avoiding this.
`...`	ignored.

Details

For matching methods other than subclassification, plot.summary.matchit uses x$sum.all[,"Std. Mean Diff."] and x$sum.matched[,"Std. Mean Diff."] as the x-axis values. For subclassification, in addition to points for the unadjusted and aggregate subclass balance, numerals representing balance in individual subclasses are plotted if subclass = TRUE in the call to summary. Aggregate subclass standardized mean differences are taken from x$sum.across[,"Std. Mean Diff."] and the subclass-specific mean differences are taken from x$sum.subclass.

Value

A plot is displayed, and x is invisibly returned.

Author(s)

Noah Greifer

Examples

data("lalonde")
m.out <- matchit(treat ~ age + educ + married +
                   race + re74, data = lalonde,
                 method = "nearest")
plot(summary(m.out, interactions = TRUE),
     var.order = "unmatched")

s.out <- matchit(treat ~ age + educ + married +
                   race + nodegree + re74 + re75,
                 data = lalonde, method = "subclass")
plot(summary(s.out, subclass = TRUE),
     var.order = "unmatched", abs = FALSE)

MatchIt

Nonparametric Preprocessing for Parametric Causal Inference

v4.1.0

GPL (>= 2)

Authors

Daniel Ho [aut] (<https://orcid.org/0000-0002-2195-5469>), Kosuke Imai [aut] (<https://orcid.org/0000-0002-2748-1022>), Gary King [aut] (<https://orcid.org/0000-0002-5327-7631>), Elizabeth Stuart [aut] (<https://orcid.org/0000-0002-9042-8611>), Alex Whitworth [ctb], Noah Greifer [ctb, cre, aut] (<https://orcid.org/0000-0003-3067-7154>)

Initial release