;+ ;procedure: crib_calc.pro ; ;purpose: demonstrate how to use the mini-language program 'calc' ; ;usage: ; .run crib_calc ; ; ;Warning: this crib uses some data from the THEMIS branch. You'll require those routines to run this crib ; ; $LastChangedBy: pcruce $ ; $LastChangedDate: 2013-12-16 16:59:54 -0800 (Mon, 16 Dec 2013) $ ; $LastChangedRevision: 13681 $ ; $URL: svn+ssh://thmsvn@ambrosia.ssl.berkeley.edu/repos/spdsoft/trunk/general/examples/crib_calc.pro $ ; ;- ;the mini-language is a language written in IDL that can be run on the ;idl virtual machine. It follows most of the syntactical rules of IDL ;with the exception that tplot variables are treated as first-class ;data types in the mini-language. They are denoted with "quotes" the ;same way that you would denote strings in normal IDL. ;All statements in the mini-language must be assignment statements ;(ie variable = expression) ;Example 1 var = number ;sets a equal to 5 calc,'a = 5' stop ;Example 2 binary operation. ;This performs multiplication on "b", you can use any of the idl ;operators with calc b = 7 calc,'seven_pi = b * 3.14159' stop ;Example 3 function/exponential notation ;This performs a function call. Also note that calc can read the same ;numerical format code as IDL. The default type, if unspecified is a ;float rather than a short int, as floats are much more common in ;scientific applications calc,'log_result = log(1e-2)' ;log base 10 calc,'log_result = ln(1e-2)' ; log base e stop ;Example 4 tvar = number ;creates a tplot variable named 'a' with the y component of its data ;struct equal to 5. Because the number 5 doesn't have any ;associated time information, neither will "a" calc,'"a"=5' stop ;Example 5 real tvar ;load some real data timespan,'2007-03-23' thm_load_state,probe='a' ;performs division on tplot variable ;Note that calc does not yet accept globbing operators ; like '?' and '*', so 'th?_state_pos' is currently an invalid name. ;We plan to add this feature soon. calc,"'tha_pos_re' = 'tha_state_pos'/6374.4" stop ;example 6 combined tvar/var ;you can combine normal and tplot variables in the same expression dpi = !DPI calc,'"tha_pos_sin" = sin("tha_pos_re"*dpi)' stop ;example 7 getting tvar data with cacl ;you can use calc as an easy way to read the data component of a tplot ;variable, after this call, data will have the data component of tha_state_pos calc,'data = "tha_state_pos"' stop ;example 8 order of operation ;calc follows the same order of operations ;and numerical type codes as IDL. If unspecified, ;the default type is float(not short int like IDL) calc,'out = 5.1 + 6.02e-3 ^ 2b * 7.6D' stop ;example 9 errors ;note that calc does not report errors by stopping execution or ;printing to the command line. If an error occurs, it returns a ;struct describing this error in a keyword called 'error' calc,'out = "?%3"',error=e help,/str,e print,e.value stop ;example 10 verbose ;you can use the /verbose option to print the error rather than return the struct calc,'out= "?%3"',/verbose stop ;example 11 function and operator lists ;calc will return a list all the available functions(and syntax) and operators calc,function_list=f,operator_list=o print,'Functions: ',f print,'Operators: ',o stop ;example 12 multi argument functions ;some functions take multiple arguments ;a second argument to 'log', is an alternate base ;also note that 'ln' is a base e logarithm calc,'log_2 = log(64,2)' stop ;example 13 more multi argument functions ;some functions take the dimension over which the operation ;should be performed calc,'t = total("tha_state_pos")' ;total over all dimensions ;t is 1 element calc,'t = total("tha_state_pos",1)' ; total over time ;t is 3 elements calc,'t = total("tha_state_pos",2)' ; total over x,y,z ;t is 1440 elements stop ;example 14 exp ;exp also takes a base as an optional argument. calc,'ex = exp(2)' ; ex = e^2 calc,'ex = exp(6,2)' ; ex = 2^6 = 64.0 calc,'ex = exp(log(64,2),2)' ; ex = 2^log_2(64) = 64 stop ;example 15 keywords ;Some functions accept keywords. Use function_list(see example above) to see syntax ;Like IDL, the keywords can be in any order, and can be abbreviated calc,'t = total("tha_state_pos",/cumulative)' ;cumulative total all dimensions ;t is 1440 x 3 elements calc,'t = total("tha_state_pos",/nan,/c,1)' ; cumulative total across time dimension, nans ignored ;t is 1440 x 3 elements calc,'t = median("tha_state_pos",2,/even)' ; median across x,y,z, using the median /even keyword(see IDL documentation) ;t is 1440 elements stop ;example 16 interpolation ;Not all tplot variables have the same cadence. ;With the interpolate keyword, calc performs interpolation automatically ;This allows data with different number of elements to be used in the same ; calculation, thm_load_fit,probe='a' calc,'"out" = "tha_state_pos" + "tha_fgs"',/interp ; interpolates to variable on the left of each binary operation("tha_state_pos" in this case) calc,'"out" = "tha_state_pos" + "tha_fgs"',interp="tha_fgs" ;interpolate to the specified variable calc,'"out" = "tha_state_pos" + "tha_fgs"',/interp,/quadratic ;can use keywords accepted by tinterpol.pro stop end