Hi Thank you so much for your help. I have put together a reproducible dataset. It would be very helpful if anyone can help how to dissolve the error. Thanks!
elabe_data <- data.frame(
DMN_vs_DMN_z = c(-1.5537227756,1.2685453317,0.5076225730,0.1588330048,0.4783086631),
HRLR = c(0, 0, 0, 0, 0),
child_sex = c(1,2,1,2,1),
mri_test_scan_day_un = c(3,1,6,6,3),
mat_med_risk_sum = c(3,1,4,3,1),
maternal_age_birth = c(25.24624, 35.86932, 26.72197, 25.94714, 27.18194),
bmi_pre_pregnancy = c(37.4,38.9,28,25.5,27.5),
modid = c('MOD1022', 'MOD1025', 'MOD1039',' MOD1054', 'MOD1058')
)
A <- lmer(elabe_data$DMN_vs_DMN_z ~ elabe_data$HRLR + elabe_data$child_sex + elabe_data$mri_test_scan_day_un + elabe_data$mat_med_risk_sum + elabe_data$maternal_age_birth + elabe_data$bmi_pre_pregnancy + (1|modid), data = elabe_data)
summary(A)
The error message is Error: number of levels of each grouping factor must be < number of observations (problems: modid).