Converting data between different formats¶
The module Convert_data contains six functions for converting data between the three formats (XCN, FNRN, FR). These functions are:
The three data formats are different ways of representing the same information. The following image shows the same data expressed in each format.
XCN - event time, censoring code, number of events - This format is the default in most commercial software including Reliasoft and Minitab. The sequence of XCN and the names may change between different software, but the format is essentially the same. Within reliability the XCN format may be reduced to XC (where all items are assumed to have quantity of 1). Some other software accepts the further reduced form of X (where there are no censored items and all items have a quantity of 1). If you have only failure data that is not grouped, then you should use the FR format as FR has a reduced form of F which is equivalent to X from XCN.
FNRN - failures, number of failures, right censored, number of right censored - This format is not used as a data entry format for reliability or any commercial software (that the author has used), but is still a valid format which combines aspects of the XCN and FR formats together. FNRN is used internally within reliability as part of the MLE algorithms.
FR - failures, right censored - This is the standard data entry format for reliability. The FR format is the most simple, but for data with many repeated values it is not as efficient at representing the data in a table as FNRN or XCN. Python has no problems performing calculations with long arrays so the FR format is chosen as the data entry format for its simplicity.
Each of the three data formats has an acceptable reduced form as follows:
- XCN reduced form is XC and all rows are assumed to have a quantity of 1
- FNRN reduced form is FN and it is assumed that there is no right censored data
- FR reduced form is F and it is assumed that there is no right censored data
For more information on these three data formats as well as how to import data from Microsoft Excel (.xlsx files) into Python, please see the section on Importing data from Excel.
For inputs and outputs see the API reference.
All of the six conversion functions contain the following methods:
- print() - this will print a dataframe of the data in the output format to the console
- write_to_xlsx() - this will export the data in the output format to an xlsx file at the specified path. Ensure you specify the path string preceeded by r to indicate raw text. For example: write_to_xlsx(path=r’C:/Users/Current User/Desktop/mydata.xlsx’). If the file already exists in the destination folder, the user will be asked (Y/N) whether they want to overwrite the existing file. If they input N then specified filename will have (new) added to the end.
In the example below we are converting FR to FNRN format and then printing each of the available outputs. Using the print() method will print a dataframe to the console.
from reliability.Convert_data import FR_to_FNRN FNRN = FR_to_FNRN(failures=[8,15,15,20,25,30,30,30,30,32,32,32], right_censored=[17,17,50,50,50,50,78,78,78,78,90]) print(FNRN.failures) print(FNRN.num_failures) print(FNRN.right_censored) print(FNRN.num_right_censored) FNRN.print() ''' [ 8 15 20 25 30 32] [1 2 1 1 4 3] [17 50 78 90] [2 4 4 1] Data (FNRN format) failures number of failures right censored number of right censored 8 1 17 2 15 2 50 4 20 1 78 4 25 1 90 1 30 4 32 3 '''
In the example below we are converting XCN to FR format. The XCN data uses censor code 1 for failures and 0 for right censored. Within reliability the default censor code for failures is 0 and for right censored is 1. If we do not correct this, the converter will interpret the censor codes the wrong way around. This is resolved by specifying the arguments censor_code and failure_code.
from reliability.Convert_data import XCN_to_FR FR = XCN_to_FR(X=[12,15,18,32,35,38,60], C=[1,1,1,0,0,0,0], N=[1,1,1,2,2,1,3], failure_code=1, censor_code=0) print(FR.failures) print(FR.right_censored) FR.print() ''' [12. 15. 18.] [32. 32. 35. 35. 38. 60. 60. 60.] Data (FR format) failures right censored 12 32 15 32 18 35 35 38 60 60 60 '''