spherical variogram model function help

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B 2017-2-25

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https://ww2.mathworks.cn/matlabcentral/answers/326900-spherical-variogram-model-function-help

回答： Vandana Rajan 2017-2-28

The variable ‘vdata’ that i loaded from my m file has two columns,the first is x and the second is y.I'm supposed to Use the nonlinear least-square tool ‘lsqcurvefit’ to estimate the two parameters ‘a’ and ‘c’, and fit a function of the form: y = c[1.5(x/a) - 0.5(x/a)^3] if x < a and y = c if x >= a

The optimum values for ‘a’ and ‘c’ are around 10 and 0.8 respectively. This is a vector minimization problem, so the initial values will be a 2-element vector.

My issue: I am supposed to write a function m-file to generate the spherical variogram using the equations above. in this prolem, y is sometimes a vector, and sometimes a scalar depending on the size of ‘a’—i have no idea how to even begin writing this. I am unsure what the variables a and c represent. any help would be appreciated on how to start writing this function

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Answer 1

Vandana Rajan 2017-2-28

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Hi,

You may check the size and type of variables inside your code, before deciding on what action to perform.

Functions like ' isscalar ' and ' isvector ' can be used to find if a variable is a scalar or a vector. To find the type of a variable, you can use ' class ' function. Also, ' cell arrays ' can be used to store elements of varying size and type. Now, if you wish to pass varying number of input arguments to a function and output varying number of arguments from a function, you can use ' varargin ' and ' varargout ' respectively.