IDL遇到的函数

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字符串

STRTRIM

The STRTRIM function removes leading and/or trailing blank from the input String.

时间

JULDAY

The JULDAY function calculates the Julian Date (which begins at noon) for the specified date. This is the inverse of the CALDAT procedure.

文件

FILE_LINES

The FILE_LINES function reports the number of lines of text contained within the specified file or files.

索引

WHERE

The WHERE function returns a vector that contains the one-dimensional subscripts of the nonzero elements of Array_Expression. The length of the resulting vector is equal to the number of nonzero elements in Array_Expression. Frequently the result of WHERE is used as a vector subscript to select elements of an array using given criteria.
Note: When WHERE Returns –1
If the NULL keyword is not set, and all the elements of Array_Expression are zero, then WHERE returns a scalar integer with a value of –1. If you use this result as an index into another array without checking for –1 first, then this will return the last element of the array. To avoid this problem, you should either use /NULL or check the Count argument before indexing.

结构

GOTO

The GOTO statement transfers program control to point specified by a label. The GOTO statement is generally considered to be a poor programming practice that leads to unwieldy programs. Its use should be avoided.