Generate bootstrap estimates for models in a list of 'lm' outputs.

## Usage

```
lm2boot_out(outputs, R = 100, seed = NULL, progress = TRUE)
lm2boot_out_parallel(
outputs,
R = 100,
seed = NULL,
parallel = FALSE,
ncores = max(parallel::detectCores(logical = FALSE) - 1, 1),
make_cluster_args = list(),
progress = TRUE
)
```

## Arguments

- outputs
A list of

`lm`

class objects, or the output of`lm2list()`

(i.e., an`lm_list`

-class object).- R
The number of bootstrap samples. Default is 100.

- seed
The seed for the random resampling. Default is

`NULL`

.- progress
Logical. Display progress or not. Default is

`TRUE`

.- parallel
Logical. Whether parallel processing will be used. Default is

`NULL`

.- ncores
Integer. The number of CPU cores to use when

`parallel`

is`TRUE`

. Default is the number of non-logical cores minus one (one minimum). Will raise an error if greater than the number of cores detected by`parallel::detectCores()`

. If`ncores`

is set, it will override`make_cluster_args`

.- make_cluster_args
A named list of additional arguments to be passed to

`parallel::makeCluster()`

. For advanced users. See`parallel::makeCluster()`

for details. Default is`list()`

.

## Value

A `boot_out`

-class object
that can be used for the `boot_out`

argument of `indirect_effect()`

,
`cond_indirect_effects()`

, and
related functions for forming
bootstrapping confidence intervals.
The object is a list with the number
of elements equal to the number of
bootstrap samples. Each element is a
list of the parameter estimates and
sample variances and covariances of
the variables in each bootstrap
sample.

## Details

This function is for
advanced users. `do_boot()`

is a
function users should try first
because `do_boot()`

has a general
interface for input-specific
functions like this one.

It does nonparametric bootstrapping
to generate bootstrap estimates of
the regression coefficients in the
regression models of a list of `lm()`

outputs, or an `lm_list`

-class object
created by `lm2list()`

. The stored
estimates can be used by
`indirect_effect()`

,
`cond_indirect_effects()`

, and
related functions in forming
bootstrapping confidence intervals
for effects such as indirect effect
and conditional indirect effects.

This approach removes the need to
repeat bootstrapping in each call to
`indirect_effect()`

,
`cond_indirect_effects()`

, and
related functions. It also ensures
that the same set of bootstrap
samples is used in all subsequent
analyses.

## Functions

`lm2boot_out()`

: Generate bootstrap estimates using one process (serial, without parallelization).`lm2boot_out_parallel()`

: Generate bootstrap estimates using parallel processing.

## See also

`do_boot()`

, the general
purpose function that users should
try first before using this function.

## Examples

```
data(data_med_mod_ab1)
dat <- data_med_mod_ab1
lm_m <- lm(m ~ x*w + c1 + c2, dat)
lm_y <- lm(y ~ m*w + x + c1 + c2, dat)
lm_out <- lm2list(lm_m, lm_y)
# In real research, R should be 2000 or even 5000
# In real research, no need to set progress to FALSE
# Progress is displayed by default.
lm_boot_out <- lm2boot_out(lm_out, R = 100, seed = 1234,
progress = FALSE)
out <- cond_indirect_effects(wlevels = "w",
x = "x",
y = "y",
m = "m",
fit = lm_out,
boot_ci = TRUE,
boot_out = lm_boot_out)
out
#>
#> == Conditional indirect effects ==
#>
#> Path: x -> m -> y
#> Conditional on moderator(s): w
#> Moderator(s) represented by: w
#>
#> [w] (w) ind CI.lo CI.hi Sig m~x y~m
#> 1 M+1.0SD 6.046 0.248 0.030 0.458 Sig 0.342 0.725
#> 2 Mean 4.990 0.024 -0.079 0.171 0.063 0.375
#> 3 M-1.0SD 3.934 -0.006 -0.087 0.098 -0.216 0.026
#>
#> - [CI.lo to CI.hi] are 95.0% percentile confidence intervals by
#> nonparametric bootstrapping with 100 samples.
#> - The 'ind' column shows the indirect effects.
#> - ‘m~x’,‘y~m’ is/are the path coefficient(s) along the path conditional
#> on the moderator(s).
#>
```