Procedure: minvar_matrix_make Purpose: tplot wrapper for minvar.pro. This routine generates a matrix or set of matrices from a time series of 3-d vector data that will transform three dimensional data into a minimum variance coordinate system. This routine takes a tplot variable that stores 3 dimensional vector data as an argument and produces a tplot variable storing the transformation matrix or matrices. The minimum variance coordinate system is taken by generating the covariance matrix for an interval of data. This matrix is then diagonalized to identify the eigenvalues and eigenvectors of the covariance matrix. The eigenvector with the smallest eigenvalue will form the direction of the z component of the new coordinate system. The eigenvector with the largest eigenvalue will form the direction of the x component of the new coordinate system. The third eigenvector will form the y direction of the coordinate system. Warning: The resulting transformation matrices will only correctly transform data from the coordinate system of the input variable to the minimum variance coordinate system. So if in_var_name is in gse coordinates then you should only use the output matrices to transform other data in gse coordinates. Arguments: in_var_name: the name of the tplot variable holding the input data, can be any sort of timeseries 3-d data tstart(optional): the start time of the data you'd like to consider for generating the transformation matrix(defaults to minimum time of in_var timeseries) tstop(optional): the stop time of the data you'd like to consider for generating the transformation matrix(defaults to maximum time of in_var timeseries) twindow(optional): the size of the window(in seconds) you'd like to consider when using a moving boxcar average to generate multiple transformations. (defaults to the entire time series) tslide(optional): the number of seconds the boxcar should slide forward after each average.(defaults to twindow/2) set tslide=0 to cause the program to generate only a single matrix newname(optional): the name of the tplot variable in which to store the transformation matrix(matrices) (defaults to in_var_name+'_mva_mat' evname(optional): the name of the tplot variable in which to store the eigenvalues of the mva matrix(matrices) (defaults to nowhere, ie if unset doesn't store them error(optional): named variable that holds the error state of the computation, 1=success 0 = failure tminname(optional): name of a tplot variable in which you would like to store the minimum variance direction vectors this vector will be represented in the original coordinate system tmidname(optional): name of a tplot variable in which you would like to store the intermediate variance direction vectors this vector will be represented in the original coordinate system tmaxname(optional): name of a tplot variable in which you would like to store the minimum variance direction vectors this vector will be represented in the original coordinate system SEE ALSO: minvar.pro tvector_rotate.pro thm_crib_mva.pro (THEMIS project) $LastChangedBy: aaflores $ $LastChangedDate: 2014-06-06 17:26:00 -0700 (Fri, 06 Jun 2014) $ $LastChangedRevision: 15328 $ $URL: svn+ssh://thmsvn@ambrosia.ssl.berkeley.edu/repos/spdsoft/trunk/general/cotrans/special/minvar/minvar_matrix_make.pro $