result of modelHomotypic(NULL) is 0

[hel404]

> modelHomotypic(NULL)
[1] 0

I've recently been using the package you developed—great work! However, when I forget to use findClusters, it still runs without errors, which prevents me from noticing my mistake.Could you please add some exception handling code?

function (annotations) 
{
    # Check if annotations is NULL or empty
    if (is.null(annotations) || length(annotations) == 0) {
        stop("Input 'annotations' cannot be NULL or empty.")
    }
    
    # Check if annotations is a vector
    if (!is.vector(annotations)) {
        stop("Input 'annotations' must be a vector.")
    }
    
    # Calculate the frequency of each annotation
    anno.freq <- table(annotations) / length(annotations)
    
    # Calculate the sum of squared frequencies
    x <- sum(anno.freq^2)
    
    # Return the result
    return(x)
}