Issues are resolved.

1. Adjust the positions of errorbars.

   Add group = FertMethod in geom_errorbar 's aes setting.

2. Adjust the widths of bars.

• When multiple bars share the same x-axis value (i.e., grouped bars), each bar appears narrower.

• When there's only one bar for a given x-axis value, it appears wider — because it's not being dodged.

  In the dataset transformation, use complete(DAS, FertMethod, Location, fill = list(MeanHeight = NA, StdError_Height = NA, MeanNode = NA, StdError_Node = NA )) .

• Due to NA, in ggplot when importing the dataset, use filter(Nutrition_FertMethod_Measurements, !is.na(MeanHeight)).