Crop Combination Analysis Concept and Calculation of Weaver՚s Method YouTube Lecture Handouts

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Combinational Analysis: Weaver, Thomas, Rafiullah - Crop Combination & Urban Area | Geography

Crop Combinations

Weaver՚s Method

Weaver՚s Method
CropBajraJowarCottonWheatMustardCastorGroundnutTur
%35.923.715.211.44.72.62.41.2

Values

Hypothetical

Observed

Difference

  • Method to find out combination of crop having significant share in total cropped area has been suggested by Weaver.
  • Compare actual area with hypothetical percentage
    • is theoretical percentage
    • is actual percentage
    • N is number of crops
  • Value of index is least for 4 crops – it would be identified as 4 crop region.
  • Thomas modified it with using crops with zero theoretical values in each step and therefore reducing need for division by n as well.

Drawbacks with Weaver՚s Model

Ignores deviation signs

  • For higher number of crops theoretical % reduces
  • Weaver՚s method (even after modification) , however, in cases of one or two functions are pre- dominantly significant and all other functions are equally insignificant, gives undue importance to the functions of very low significance. In many empirical problems, therefore, Weaver՚s method does not give intuitively correct results.
  • The basic reason of this fallacy in Weaver՚s method as pointed out by Rafiullah is that:
    • it ignores the signs of the deviations, and
    • for a higher number of crops or functions the theoretical percentages go down and so the deviations caused by last values are under - estimated.
  • While applying Weaver՚s method for functional classification of towns, Rafiullah suggested another modification in it. His modified index is given as:
  • Where Dp and Dn are the sum of squares of positive and negative deviations from the middle of the theoretical values.
  • Here the maximum values gives the critical combination.

Crop Combinations Modifications by Thomas & Rafiullah

Thomas Method

Thomas Method
CropBajraJowarCottonWheatMustardCastorGroundnutTur
%35.923.715.211.44.72.62.41.2
  • Method to find out combination of crop having significant share in total cropped area has been suggested by Weaver.
  • Compare actual area with hypothetical percentage
    • is theoretical percentage
    • is actual percentage
    • N is number of crops
  • Value of index is least for 4 crops – it would be identified as 4 crop region.
  • Thomas modified it with using crops with zero theoretical values in each step and therefore reducing need for division by n as well.

Rafiullah՚s Modification

  • Weaver՚s method (even after modification) , however, in cases of one or two functions are pre- dominantly significant and all other functions are equally insignificant, gives undue importance to the functions of very low significance. In many empirical problems, therefore, Weaver՚s method does not give intuitively correct results.
  • The basic reason of this fallacy in Weaver՚s method as pointed out by Rafiullah is that:
    • it ignores the signs of the deviations, and
    • for a higher number of crops or functions the theoretical percentages go down and so the deviations caused by last values are under - estimated.
  • While applying Weaver՚s method for functional classification of towns, Rafiullah suggested another modification in it. His modified index is given as:
  • Where Dp and Dn are the sum of squares of positive and negative deviations from the middle of the theoretical values.
  • Here the maximum values gives the critical combination.

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