Is IDL 8.5 able to read tables with strings, dates and values in it? - idl-programming-language

Question

I am very new in the IDL scene and I am struggling for hours with a problem and I hope you can help me:
So right now I am trying to read data from a table ("file.txt"). I would like, that every column is saved in a variable (I thought about using STRARR)
I found this tutorial: http://www.idlcoyote.com/tips/ascii_column_data.html
This is very useful, when you want to read numbers for every column, which works fine.
This is the table from the tutorial above:
Tutorial table:
Experiment 01-14-97-2b9c
No. of Data Rows: 5
Temperature Pressure Relative Humidity
20.43 0.1654 0.243
16.48 0.2398 0.254
17.21 0.3985 0.265
18.40 0.1852 0.236
21.39 0.2998 0.293
Code:
OPENR, lun, "tutorial.txt", /GET_LUN
header = STRARR(3)
READF, lun, header
data = FLTARR(3, 5)
READF, lun, data
temperature = data(0,*)
print, data
print, temperature
Output data:
20.4300 0.165400 0.243000
16.4800 0.239800 0.254000
17.2100 0.398500 0.265000
18.4000 0.185200 0.236000
21.3900 0.299800 0.293000
Output temperature:
20.4300
16.4800
17.2100
18.4000
21.3900
Looks quite good, for numbers.
But what about when I have strings with dates, times, but also numbers in it, like this:
My table:
Experiment 01-14-97-2b9c
No. of Data Rows: 5
Date Start time End time Value
12-Feb-2002 05:08:10 06:08:30 20
08-Mar-2002 07:35:38 09:25:59 100
20-Jun-2002 12:30:35 16:15:18 5536
25-Jul-2002 04:02:06 07:02:58 5822
02-Aug-2002 23:30:25 23:55:22 456
The code above won't work anymore. When I am using this my_var= data(0,*), the whole data will be saved in variable my_var, of course because the data are no more looking as columns, but in a whole row.
FLTARR is setting this data
12-Feb-2002 05:08:10 06:08:30 20
to this result (of course because of FLTarr)
12.0000
5.00000
6.00000
20.0000
And STRARR is saving the data good in my_var, but without separating the columns.
What I want:
I would like to have every column in one variable, so that I can handle these variable data later in another code.
dates = data(0,*)
starts = data(1,*)
ends = data(2,*)
values = data(3,*)
print, starts
Output:
Start time
05:08:10
07:35:38
12:30:35
04:02:06
23:30:25
(and also the rest of my variables)
I hope you can help here.
Maybe I misunderstood something, if so please let me know it.
For any other suggestion or solution I would be grateful.
Thanks in advance!

Answer 1

My suggestion would be to use STRSPLIT in some manner, either each line as you read it or all at the end.
Here is an example of doing it all at the end. First, read the data into a data array (ignoring the header array):
IDL> openr, lun, 'file.txt', /get_lun
IDL> header = strarr(3)
IDL> readf, lun, header
IDL> data = strarr(5)
IDL> readf, lun, data
IDL> free_lun, lun
Then split on whitespace:
IDL> tokens = strsplit(data, /extract)
And, finally, extract elements by position:
IDL> dates = (tokens.map(lambda(x: x[0]))).toarray()
IDL> starts = (tokens.map(lambda(x: x[1]))).toarray()
IDL> ends = (tokens.map(lambda(x: x[2]))).toarray()
IDL> values = (tokens.map(lambda(x: long(x[3])))).toarray()
You've got your values now:
IDL> help, dates, starts, ends, values
DATES STRING = Array[5]
STARTS STRING = Array[5]
ENDS STRING = Array[5]
VALUES LONG = Array[5]
IDL> print, values
20 100 5536 5822 456
UPDATE: Make sure you have done
IDL> compile_opt strictarr
in scope before these commands.
UPDATE: To sort these arrays by value:
IDL> ind = sort(values)
IDL> values = values[ind]
IDL> dates = dates[ind]
IDL> starts = starts[ind]
IDL> ends = ends[ind]