# Correlation Analysis with manymodelr

#### 2025-08-22

- `get_var_corr`

As can probably(hopefully) be guessed from the name, this provides a convenient way to get variable correlations. It enables one to get correlation between one variable and all other variables in the data set.

Previously, one would set `get_all` to `TRUE` if they wanted to get correlations between all variables. This argument has been dropped in favor of simply supplying an optional `other_vars` vector if one does not want to get all correlations.

    library(manymodelr)
    #> Welcome to manymodelr. This is manymodelr version 0.4.0.
    #>  Please file issues and feedback at https://www.github.com/Nelson-Gon/manymodelr/issues
    #> Turn this message off using 'suppressPackageStartupMessages(library(manymodelr))'
    #>  Happy Modelling! :)
    # getall correlations

    # default pearson

    head( corrs <- get_var_corr(mtcars,comparison_var="mpg") )
    #>   comparison_var other_var      p.value correlation    lower_ci   upper_ci
    #> 1            mpg       cyl 6.112687e-10  -0.8521620 -0.92576936 -0.7163171
    #> 2            mpg      disp 9.380327e-10  -0.8475514 -0.92335937 -0.7081376
    #> 3            mpg        hp 1.787835e-07  -0.7761684 -0.88526861 -0.5860994
    #> 4            mpg      drat 1.776240e-05   0.6811719  0.43604838  0.8322010
    #> 5            mpg        wt 1.293959e-10  -0.8676594 -0.93382641 -0.7440872
    #> 6            mpg      qsec 1.708199e-02   0.4186840  0.08195487  0.6696186

Previously, one would also set `drop_columns` to `TRUE` if they wanted to drop factor columns. Now, a user simply provides a character vector specifying which column types(classes) should be dropped. It defaults to `c("character","factor")`.

    data("yields", package="manymodelr")
    # purely demonstrative
    get_var_corr(yields,"height",other_vars="weight",
                 drop_columns=c("factor","character"),method="spearman",
                 exact=FALSE)
    #> Warning in get_var_corr.data.frame(yields, "height", other_vars = "weight", :
    #> Columns with classes in drop_columns have been discarded. You can disable this
    #> yourself by setting drop_columns to NULL.
    #>   comparison_var other_var      p.value correlation
    #> 1         height    weight 4.204642e-07  -0.1591719

Similarly, `get_var_corr_` (note the underscore at the end) provides a convenient way to get combination-wise correlations.

    head(get_var_corr_(yields),6)
    #> Warning in get_var_corr_.data.frame(yields): Columns with classes in
    #> drop_columns were dropped.
    #>   comparison_var other_var      p.value correlation    lower_ci    upper_ci
    #> 1         height    weight 1.470866e-08 -0.17793196 -0.23730741 -0.11723201
    #> 2         height     yield 4.473683e-01  0.02405390 -0.03799584  0.08591886
    #> 3         weight     yield 2.986171e-01  0.03290108 -0.02915146  0.09470100

To use only a subset of the data, we can use provide a list of columns to `subset_cols`. By default, the first value(vector) in the list is mapped to `comparison_var` and the other to `other_Var`. The list is therefore of length 2.

    head(get_var_corr_(mtcars,subset_cols=list(c("mpg","vs"),c("disp","wt")),
                       method="spearman",exact=FALSE))
    #>   comparison_var other_var      p.value correlation
    #> 2            mpg      disp 6.370336e-13  -0.9088824
    #> 5            mpg        wt 1.487595e-11  -0.8864220

- `plot_corr`

Obtaining correlations would mostly likely benefit from some form of visualization. `plot_corr` aims to achieve just that. There are currently two plot styles, `squares` and `circles`. `circles` has a `shape` argument that can allow for more flexibility. It should be noted that the correlation matrix supplied to this function is an object produced by `get_var_corr_`.

To modify the plot a bit, we can choose to switch the x and y values as shown below.

    plot_corr(mtcars,show_which = "corr",
              round_which = "correlation",decimals = 2,x="other_var",  y="comparison_var",plot_style = "squares"
              ,width = 1.1,custom_cols = c("green","blue","red"),colour_by = "correlation")
    #> Warning in plot_corr(mtcars, show_which = "corr", round_which = "correlation",
    #> : Using colour_by for the legend title.

To show significance of the results instead of the correlations themselves, we can set `show_which` to “signif” as shown below. By default, significance is set to 0.05. You can override this by supplying a different `signif_cutoff`.

    # color by p value
    # change custom colors by supplying custom_cols
    # significance is default
    set.seed(233)
    plot_corr(mtcars, x="other_var", y="comparison_var",plot_style = "circles",show_which = "signif", colour_by = "p.value", sample(colours(),3))
    #> Warning in plot_corr(mtcars, x = "other_var", y = "comparison_var", plot_style
    #> = "circles", : Using colour_by for the legend title.

To explore more options, please take a look at the documentation.