CDF_EPOCH_COMPARE ================= The CDF_EPOCH_COMPARE function compares two epoch (date and time) values. Values can be scalars or an array of values. The epoch can be one of the CDF formats, CDF_EPOCH, CDF_EPOCH16 or CDF_TIME_TT2000. While data of type CDF_EPOCH and CDF_EPOCH16 can be compared with each other, data in CDF_TIME_TT2000 can be compared only with data of the same type. If the base epoch is a scalar, it is used to compare with all values in the first epoch. If the base epoch is an array, the same element in the source and base epoch array is compared. If a third argument, endepoch, is provided, the baseepoch and endepoch are used as the starting and ending epoch that the source epoch will be checked against. The procedure allows input of an array of values to compare. Initially, it can only handle a scalar. Examples ; For CDF_EPOCH data type CDF_VARGET, id, "Epoch", ep, REC_COUNT=1000,/ZVARIABLE CDF_EPOCH, base, 2005,6,1,10,18,17,2,/COMPUTE ret= CDF_EPOCH_COMPARE(ep,base) HELP, ret ; For CDF_TIME_TT2000 data type CDF_VARGET, id2, "Epoch", ep2, REC_COUNT=1000,/ZVARIABLE CDF_TT2000, base2, 2005,6,1,10,18,17,2,3,4,/COMPUTE ret2= CDF_EPOCH_COMPARE(ep2,base2) HELP, ret2 ; For CDF_EPOCH data type CDF_VARGET, id3, "Epoch", ep3, REC_COUNT=1000,/ZVARIABLE CDF_EPOCH, starting, 2005,6,1,10,18,17,2,/COMPUTE CDF_EPOCH, ending, 2005,6,10,10,18,17,2,/COMPUTE ret3= CDF_EPOCH_COMPARE(ep3,starting,ending) HELP, ret3 Syntax Result = CDF_EPOCH_COMPARE(epoch, baseepoch, [endepoch]) Return Value Using Two Arguments If the function uses two arguments, the return value is a scalar value or an array of integer values (1, 0, or -1), depending on the source epoch. If the value of the first epoch is greater (later date and time) than the base epoch, 1 is set. If the value of the first epoch is the same as the base epoch, 0 is set. If the value of the first epoch is less (earlier date and time) than the base epoch, -1 is set. Result Condition 1 if epoch1 > baseepoch 0 if epoch1 = baseepoch -1 if epoch1 < baseepoch Using Three Arguments If the function uses three arguments, the return value is a scalar value or an array of integer values (1 or 0). If the value of the source epoch falls within the starting and ending epoch, 1 is set. Otherwise, 0 is set. 1 if baseepoch <= epoch1 <= endepoch 0 Otherwise Arguments epoch A single or an array of epoch value(s) returned from: CDF_EPOCH,/compute, CDF_EPOCH16,/compute for CDF_EPOCH or CDF_EPOCH16 data type CDF_TT2000,/compute for CDF_TIME_TT2000 data type CDF_VARGET, or CDF_VARGET1 baseepoch A single or an array of epoch value(s) returned from: CDF_EPOCH,/compute, CDF_EPOCH16,/compute for CDF_EPOCH or CDF_EPOCH16 data type CDF_TT2000,/compute for CDF_TIME_TT2000 data type CDF_VARGET, or CDF_VARGET1 endepoch A single or an array of epoch value(s) returned from: CDF_EPOCH,/compute, CDF_EPOCH16,/compute for CDF_EPOCH or CDF_EPOCH16 data type CDF_TT2000,/compute for CDF_TIME_TT2000 data type CDF_VARGET, or CDF_VARGET1 Note: This field must be of the same data type and dimensionality as baseepoch. Keywords None Version History 6.4 Introduced © 2015 Exelis Visual Information Solutions, Inc., a subsidiary of Harris Corporation. All Rights Reserved. This information is not subject to the controls of the International Traffic in Arms Regulations (ITAR) or the Export Administration Regulations (EAR). However, this information may be restricted from transfer to various embargoed countries under U.S. laws and regulations.