When dealing with many DOIs and when no metrics has been found for some of them (ie the list element is NULL), the altmetric_data function throws an error about the raw_metrics list:
metric_data <- ldply(raw_metrics, altmetric_data)
Error in class(output[[var]]) <- class(value) :
attempt to set an attribute on NULL
When dealing with many DOIs and when no metrics has been found for some of them (ie the list element is NULL), the altmetric_data function throws an error about the raw_metrics list:
Error in class(output[[var]]) <- class(value) : attempt to set an attribute on NULL