Reads in summary data. Checks and organises columns for use in calculating multivariable Mendelian Randomization analyses. Where variant IDs are not provided, a vector is generated for variant identification.

## Arguments

- BXGs
A matrix containing beta-coefficient values for genetic associations with the each exposure. Columns should indicate exposure number, with rows representing estimates for a given genetic variant.

- BYG
A numeric vector of beta-coefficient values for genetic associations with the outcome.

- seBXGs
A matrix containing standard errors corresponding to the matrix of beta-coefficients

`BXGs`

.- seBYG
A numeric vector of standard errors corresponding to the beta-coefficients

`BYG`

.- RSID
A vector of names for genetic variants included in the analysis. If variant IDs are not provided (

`RSID="NULL"`

), a vector of ID numbers will be generated.

## References

Sanderson, E., et al., An examination of multivariable Mendelian randomization in the single-sample and two-sample summary data settings. International Journal of Epidemiology, 2019, 48, 3, 713-727. doi:10.1093/ije/dyy262

## Examples

```
r_input <- format_mvmr(
BXGs = rawdat_mvmr[,c("LDL_beta","HDL_beta")],
BYG = rawdat_mvmr$SBP_beta,
seBXGs = rawdat_mvmr[,c("LDL_se","HDL_se")],
seBYG = rawdat_mvmr$SBP_se,
RSID = rawdat_mvmr$SNP)
names(r_input)
#> [1] "SNP" "betaYG" "sebetaYG" "betaX1" "betaX2" "sebetaX1" "sebetaX2"
class(r_input)
#> [1] "data.frame" "mvmr_format"
```