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TI03-DataExtractor/trunk/pydxs/NumericalOperations.py
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Subversion URL: http://proj.badc.rl.ac.uk/svn/ndg/TI03-DataExtractor/trunk/pydxs/NumericalOperations.py@794
Revision 794, 4.0 KB checked in by astephen, 14 years ago (diff) |
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1 | # Copyright (C) 2004 CCLRC & NERC( Natural Environment Research Council ). |

2 | # This software may be distributed under the terms of the |

3 | # Q Public License, version 1.0 or later. http://ndg.nerc.ac.uk/public_docs/QPublic_license.txt |

4 | |

5 | """ |

6 | NumericalOperations.py |

7 | ====================== |

8 | |

9 | Holds the NumericalOperations class used to perform various |

10 | mathematical operations involving one or more variables. |

11 | |

12 | """ |

13 | |

14 | # Import library modules |

15 | import os, sys, re |

16 | |

17 | # Import external modules |

18 | import cdms |

19 | |

20 | # Import package modules |

21 | from serverConfig import * |

22 | from common import * |

23 | |

24 | class NumericalOperations: |

25 | """ |

26 | Class used to perform various mathematical operations involving one or |

27 | more variables. |

28 | """ |

29 | |

30 | def __init__(self, opstring): |

31 | """ |

32 | Method to take in the operation string and map it to an operation using |

33 | variables provided. |

34 | """ |

35 | operation=self._parseOperation(opstring) |

36 | |

37 | |

38 | def _parseOperation(self, opstring): |

39 | """ |

40 | Parses the operation string. |

41 | """ |

42 | matchedIndices=re.findall(r"\(variable(\d+)\)", opstring) |

43 | self.variableIndices=[int(i)-1 for i in matchedIndices] |

44 | if opstring=="(variable2)-(variable1)": |

45 | self.opMethod=self.var2_minus_var1 |

46 | elif opstring=="(variable1)-(variable2)": |

47 | self.opMethod=self.var1_minus_var2 |

48 | |

49 | |

50 | def performOperation(self, varList): |

51 | """ |

52 | Calls appropriate method to actually perform operation. |

53 | """ |

54 | apply(self.opMethod, (varList,)) |

55 | |

56 | |

57 | def _chooseOperation(self, opstring): |

58 | """ |

59 | Method to map operation string to a known method. |

60 | """ |

61 | if opstring=="var1 - var2": |

62 | method=self.v1minusv2 |

63 | elif opstring=="var2 - var1": |

64 | method=self.v2minusv1 |

65 | elif opstring=="var1 + var2": |

66 | method=self.v1addv2 |

67 | elif opstring=="var1 * var2": |

68 | method=self.v1timesv2 |

69 | elif opstring=="var1 / var2": |

70 | method=self.v1dividedbyv2 |

71 | elif opstring=="var2 / var1": |

72 | method=self.v2dividedbyv1 |

73 | elif opstring=="((var1**2) + (var2**2))**0.5": |

74 | method=self.magv1v2 |

75 | elif opstring=="var1, var2 (as they come)": |

76 | method=self.v1andv2 |

77 | return method |

78 | |

79 | |

80 | def processOperation(self, variables): |

81 | """ |

82 | Method to actually process the operation. |

83 | """ |

84 | vars=self.operation() |

85 | return vars |

86 | |

87 | |

88 | def var2_minus_var1(self, varList): |

89 | """ |

90 | Method to subtract var1 from var2. Returns the resulting array |

91 | as a transient variable. |

92 | """ |

93 | varList.reverse() |

94 | return self.var1_minus_var2(varList) |

95 | |

96 | |

97 | def var1_minus_var2(self, varList): |

98 | """ |

99 | Method to subtract var2 from var1. Returns the resulting array |

100 | as a transient variable. |

101 | """ |

102 | (var1, var2)=varList |

103 | |

104 | if compareGrids(var1.getGrid(), var2.getGrid())==0: |

105 | # Use the standard CDAT regridder to interpolate variable 2 to variable 1 grid. |

106 | # This might be replaced by the SCRIP regridder (or other) in future. |

107 | if var1.rank()!=var2.rank(): |

108 | var1=var1(squeeze=1) |

109 | var2=var2(squeeze=1) |

110 | #print var1, var2 |

111 | try: |

112 | var1Grid=var1.getGrid() |

113 | var2Grid=var2.getGrid() |

114 | v1Size=var1Grid.size() |

115 | v2Size=var2Grid.size() |

116 | if v1Size>=v2Size: |

117 | var1=var1.regrid(var2Grid) |

118 | else: # v2Size>v1Size |

119 | var2=var2.regrid(var1Grid) |

120 | |

121 | except Exception, error: |

122 | raise DXProcessingError, "An error occurred whilst trying to interpolate variables to same grid." |

123 | |

124 | print "Differencing datasets..." |

125 | |

126 | # Subtract var2 from var1 |

127 | array=var1-var2 |

128 | |

129 | # Create some metadata for the new variable name |

130 | rtVar=cdms.createVariable(array, grid=var1.getGrid()) |

131 | rtVar.name="Differenced dataset: %s - %s" % (var1.id, var2.id) |

132 | rtVar.long_name=rtVar.name |

133 | rtVar.title=rtVar.name |

134 | rtVar.id="%s_minus_%s" % (var1.id, var2.id) |

135 | if hasattr(rtVar, "units"): del rtVar.units |

136 | |

137 | return rtVar |

138 | |

139 | |

140 | if __name__=="__main__": |

141 | x=NumericalOperations("(variable1)-(variable2)") |

142 | print x.variableIndices |

143 | print x.opMethod |

144 | print x.performOperation([cdms.open("/usr/local/dx/testdata/testdata1.xml")("pqn", time=slice(0,1)), cdms.open("/usr/local/dx/testdata/testdata2.xml")("var2")]) |

145 |

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