"generate a sublist from the weight object based on the weight value"

I applied 'weight by information gain" for the feature selection. The generated weight object is a two column attribute. Assume the whole weight list has 2000 elements. The following figure is just a screen shot. Is that possible for me to select the top 50 elements based on the weight? For instance, I only want to generate a attribute list with 50 elements which are ranked as top 50 in the original weight object.

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