Write text file idl

If no output width is specified, IDL uses the following rules to determine where to break lines:. Use XDR to make binary data portable between different machine architectures by reading and writing all data in a standard format.

The floating-point number format used by a program such as IDL is determined entirely by the computer hardware upon which it runs. In the early years of computing it was common for different machines to have incompatible floating-point formats. In the s and s, PDP and VAX minicomputers were widely used for scientific computation, and their floating-point format known as VAX F and D floating became the de facto standard for science. Early versions of IDL used these formats.

Now, all common computing hardware uses the IEEE format, which has significant advantages over earlier formats:. This convergence gained momentum in the s as workstations and personal computers came into prominence. Despite the almost universal current use of the IEEE format, valuable older data stored in the VAX floating-point formats exists at various scientific institutions around the world.

In order to allow access to this data, IDL is able to read and write data in these formats. When converting between VAX and IEEE formats, you should be aware of the following basic numerical issues in order to get the best results. There are many cases where the recovered values will differ from the original values, including:.

As a practical matter, an initial conversion of existing VAX format data to IEEE cannot be avoided if the data is to be used on modern machines. However, each format conversion can add a small amount of error to the resulting values, so it is important to minimize the number of such conversions.

Create all new files using the native IEEE format. This introduces only a single unavoidable conversion, and minimizes the resulting conversion error. Search Results. If the file exists, it is truncated and its old contents are destroyed. Examples The following example opens the IDL distribution file people. File A string containing the name of the file to be opened.

Data 8. Set this keyword equal to an array of strings that will be inserted at the beginning of the CSV file, one string per line. The IDL Workbench. Search Results. Data Data 8 The data values to be written out to the CSV file.

You can tell readcol to look for text in a given column by including the format statement. This command tells readcol to look for floating-point numbers in the first two columns, but text a scii in the third column. Formatted Output with Writecol. Writecol behaves similarly: the expectation is that you are writing columns of numbers. To force an output column to be ascii,. Notice that the keyword changes from format to fmt for no good reason.

The ' x' in the format statement asks writecol to put in a blank space between y and names. The Hard Way. You will run into limitations with readcol and writecol , in which case you'll have to do things the hard way.

Files are handled by assigning them a "logical unit number," or LUN. I'll just give you some simple examples, using the lambda and signal data we already have loaded. Here's an procedure that would read the spectrum from an external file. Here, I'm storing the LUN in the variable "in.