Histrogram with Linq

Question

Is there a way to do a segmented histrogram with linq? I've seen several examples where you can count the number of occurances of a particular object. Is it possible to create a linq based historgram that counts the number of occurances of a series of objects between two values?

I don't know how you would group by a range of items to create the buckets neccesary for a histogram? Suppose a start bound and a width are used to create the range.

You would need to iterate through the number array and group each number by whether it was <= Upper Bound and > Lower Bound. Then you would just sum each group. I have no idea how to accomplish the group by part

Answer 1

Something like this?

        Random randF = new Random();
        List<double> nums = new List<double>();
        for (int i = 0; i < 100000; i++)
        {
            nums.Add(randF.NextDouble()*100);
        }

        double fromXF = 30;
        double toXF = 80;
        int groupCount = 10; // number of groups between values
        var histF = from i in nums
                    let groupKeyF = ((i-fromXF)/(toXF-fromXF)*groupCount) // even distribution of "groupCount" groups between fromXF and toXF, simple math, really
                    where groupKeyF >= 0 && groupKeyF < groupCount // only groups we want
                    let groupKey = (int)groupKeyF // clamp it to only group number
                    group i by groupKey into gr  // group it according to group number
                    orderby gr.Key
                    select new { Value = gr.Key, Count = gr.Count() };

        foreach (var item in histF)
        {
            Console.WriteLine("Group number: " + item.Value + ", Count: " + item.Count);
        }

Answer 2

You could do something like:

var groups = input.GroupBy(x => (int)((x.value - start)/width));

which creates an integer value for each bar and groups by that.