But if I wanted the date in separate year, month, and day variables as integersI think I would do it like this. First, you must attach the file to a logical unit idl write ascii columns, since all file input and output occurs over logical unit numbers in IDL.
The method shown here requires that you know that the integer specifying how many rows of data there are in the file starts on 18th column in the file see the FORMAT keyword, below.
The preferred way to read this data is like this: How can I read this kind of data file in IDL? Or, you can read a longer answer here.
You would set your structure up as appropriate for your data file. Since in this case you know that the header is the first three lines of the file, you can read the header into a three-element string array.
The code looks like this: PRINT, header The next step is to read the number of rows in the data file from the second line of the header. Consider a file, named test.
If the last dimension of a multiply-dimensioned array is 1, IDL drops that dimension. Next, we have to create an array of these structures, one for each row of data.
When reading a string variable, IDL reads until the end of the current line in the file. You can use array subscripting for this task, like this: Thus, these arrays become normal one-dimensional row vectors.
There are any number of ways to read this type of data file in IDL, but here is one way. You could read values into temporary variables, and store them in your loop if you like.
Just read the data. For example, if you want to print out all the dates in the file, you would do this. These three vectors can be turned into row vectors by using the REFORM command to dimension them into a rows-by-1 array.
IDL was designed as an array processing language and it excells at handling data arrays all at once rather than in loops. The first few lines of the data file look like this: We can use the Replicate command to do this. With the number of rows known, it might occur to you especially if you are a FORTRAN programmer that you can initialize the three vectors you are after and read them directly, like this: Our first task is to create a structure to represent each row of data.
Or the number of rows will be variable. Now you are ready to read the data itself.
Your code might look like this: The number of rows in the data file is variable, but the number is written in the second line of the header. It would be better to read the data all at once and use array processing techniques to pull the vectors out of the larger array.
The logical unit number will be assigned to the variable lun in the command below. What do you do then? I might have set my code up like this: I want each column to be a separate IDL vector. Normally, when you think of a vector in IDL you think of a row vector.Reading ASCII Data Files.
QUESTION: I have an ASCII data file named mint-body.com with a three line header and three columns of data.
I want each column to be a separate IDL vector. The number of rows in the data file is variable, but the number is written in the second line of the header. FITS I/O in the IDL Astronomy Library FITS (Flexible Image Transport System) is a standardized data format which is widely used in astronomy.
Although originally conceived as simply a standard interchange format for digital images, FITS files are now often used as a working data format, and can be used to store ASCII or binary tabular data, in.
Brief Recap from Beginner's IDL I. Before diving into data input and output in IDL, consider the methods we discussed before. How to read and write files. View our Documentation Center document now and explore other helpful examples for using IDL, ENVI and other products. WRITE_CSV Welcome to the Harris Geospatial product documentation center.
View our Documentation Center document now and explore other helpful examples for using IDL, Allows you to specify the starting location (in columns) for each field when using fixed width fields. When importing an ASCII data file into IDL, you must first describe the format of the data using the interactive ASCII_TEMPLATE function.
Reading and Writing Ascii Files Page history last edited by Robert da Silva 7 to handle up to columns, you can find the new version in Slug IDL Code.
Reading Arbitary Ascii Files. You first need to open up the file. This is done with the following commnand Writing Ascii Files. Analogous to how we write files, we first need to open a.Download