input and output i: ascii and binary files. data formats ascii binary netcdf hdf

Input and Output I: ASCII and Binary files

Data formats

• ASCII• Binary• netCDF• HDF

Write to screen• Syntax:

print, arg1, arg2, …, argn

print, arg1, arg2, …, argn, format=‘(format code)’

print, arg1, arg2, …, argn, format=‘(N(format code))’

• Format codes (iN, fN.M, eN.M, aN) print, !pi, format=‘(i1)’

print, !pi, format=‘(f5.2)’

print, !pi, format=‘(e6.2)’

print, string(!pi, format=‘(a5)’)

• Notes on format codes: 1) Always used from left to right

2) If there are more codes than values, the left codes are not used

3) If there are less codes than values, then after all codes are used, a new line is printed and the codes are repeated

Read from keyboard• Syntax:

read, arg1, arg2, …, argn

read, arg1, arg2, …, argn, format=‘(format code)’

read, arg1, arg2, …, argn, format=‘(N(format code))’

• Note: Please remember to define the variables before using them to read in data

Open/close a file• Two types of files: Formatted: ascii format Unformatted: binary format• Open a file for read only: openr, lun, filename (lun is the logical unit number, could be set as 1-99) openr, 5, ‘test.dat’• Open a file for read or write: openw, lun, filename• Close a file: Please remember to close a file after

finishing reading/writing close, lun• Check for end-of-file: eof(lun) (=1, end; =0 not end)

Reading and writing ascii files• Syntax:

readf, lun, arg1, arg2, …, argn, format=‘(format code)’

printf, lun, arg1, arg2, …, argn, format=‘(format code)’• Example

p=1000.0

T=29.5

openw, 1, ‘t.dat’

printf, 1, ‘Pressure’, p, ‘Temperature’, T, format=‘(a15, f8.1, a15, f8.1)’

close, 1

a2=‘ ’

b2=‘ ’

p2=0.0

t2=0.0

openr, 2, ‘t.dat’

readf, 2, a2, p2, b2, t2, format=‘(a15, f8.1, a15, f8.1)’

print, a2, p2, b2, t2

close, 2

Check if you read the data correctly

• Print the value of one variable• Print the maximum, minimum, mean, median

values• Plot the time series• Plot spatial distribution along a longitude or

latitude or height• Plot horizontal distribution using contour map

Reading/writing binary files• Syntax: readu, lun, arg1, arg2, …, argn (compatible w/ Fortran-77 unformatted direct access

mode) readu, lun, arg1, arg2, …, argn, /f77_unformatted (compatible w/ Fortran-77 unformatted sequential

access mode)• To read portable binary file: add /xdr readu, lun, arg1, arg2, …, argn, /xdr If you don’t know if the data file is in portable format

or not, you can try adding/removing /xdr • Note: Binary format is generally machine-

dependent, so please try to avoid writing data into binary files. You can use netCDF files instead if you want to reduce the file size.

Contour

• Syntax: contour, d, x, y x(nx) x ordinate y(ny) y ordinate d(nx, ny) data array

contour, d (the data points are plotted against corresponding array indices)

Contour customization• Keywords

xyouts• Syntax:

xyouts, x, y, string

where

x is x ordinate

y is y ordinate

string is the string you want to overplot

In-class assignment VData files are stored at: http://lightning.sbs.ohio-state.edu/geo820/data/1. Read the ascii file sonde.ascii for sounding data from

tropical station Chuuk. Read and plot the profiles of pressure (pres), height (hght), temperature (temp), and mixing ratio (mixr) for the first sounding

2. (Bonus) Could you find a way to automatically read all the soundings in this file?

3. Read the binary file precip.bin for GPI global satellite precipitation data. The readme file is precip.readme. Note you may need to check if it is in portable format. Use different methods to check if you read the data correctly.

4. Make a contour plot of the long-term mean of GPI global precipitation. Use xyouts to show the location of Columbus, OH