Example: Reading Formatted Table Data
IDL explicitly formatted input/output has the power and flexibility to handle almost any kind of formatted data. A common use of explicitly formatted input/output involves reading and writing tables of data. Consider a data file containing employee data records. Each employee has a name (String, 32 columns) and the number of years they have been employed (Integer, 3 columns) on the first line. The next two lines contain each employee's monthly salary for the last twelve months. A sample file named employee.dat with this format might look like the following:
Bullwinkle 10 1000.0 9000.97 1100.0 2000.0 5000.0 3000.0 1000.12 3500.0 6000.0 900.0 Boris 11 400.0 500.0 1300.10 350.0 745.0 3000.0 200.0 100.0 100.0 50.0 60.0 0.25 Natasha 10 950.0 1050.0 1350.0 410.0 797.0 200.36 2600.0 2000.0 1500.0 2000.0 1000.0 400.0 Rocky 11 1000.0 9000.0 1100.0 0.0 0.0 2000.37 5000.0 3000.0 1000.01 3500.0 6000.0 900.12
The following IDL statements read data with the above format and produce a summary of the contents of the file:
;Open data file for input. OPENR, 1, 'employee.dat' ;Create variables to hold the name, number of years, and monthly ;salary. name = '' & years = 0 & salary = FLTARR(12) ;Output a heading for the summary. PRINT, FORMAT='("Name", 28X, "Years", 4X, "Yearly Salary")' ;Note: The actual dashed line is longer than is shown here. PRINT, '========' ;Loop over each employee. WHILE (~ EOF(1)) DO BEGIN ;Read the data on the next employee. READF, 1, $ FORMAT = '(A32,I3,2(/,6F10.2))', name, years, salary ;Output the employee information. Use TOTAL to sum the monthly ;salaries to get the yearly salary. PRINT, FORMAT='(A32,I5,5X,F10.2)', name, years, TOTAL(salary) ENDWHILE CLOSE, 1
The output from executing these statements on employee.dat is as follows:
Name Years Yearly Salary ====================================================== Bullwinkle 10 32501.09 Boris 11 6805.35 Natasha 10 14257.36 Rocky 11 32500.50
