Tests how often the SNP-exposure and SNP-outcome signs are concordant This is to avoid the problem of averaging over all SNPs, which can suffer bias due to outliers with strong effects; and to avoid excluding SNPs which is implicit in median and mode based estimators The effect estimate here is not to be interpreted as the effect size - it is the proportion of SNP-exposure and SNP-outcome effects that have concordant signs. e.g. +1 means all have the same sign, -1 means all have opposite signs, and 0 means that there is an equal number of concordant and discordant signs. Restricted to only work if there are 6 or more valid SNPs

mr_sign(b_exp, b_out, se_exp = NULL, se_out = NULL, parameters = NULL)

## Arguments

b_exp Vector of genetic effects on exposure Vector of genetic effects on outcome Not required Not required Not required

## Value

List with the following elements:

b

Concordance (see description)

se

NA

pval

p-value

nsnp

Number of SNPs (excludes NAs and effect estimates that are 0)