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Exchanging Data Files between SIGNAL and MATLAB

Application Note 11 5

Exporting MATLAB floating point time and frequency files to

SIGNAL

MATLAB values are stored in floating point format, so all MATLAB data is exported as

headerless files in 32-bit floating point format. When reading these files, SIGNAL will query

the user to establish the time base of the data, since there is no file header to convey this:

Buffer

type Query parameters

T, F Sample rate

FT Sample rate, time range, no. time bins

1. The following will write the entire one-dimensional array A to the headerless floating

point file RFILE:

fid = fopen ('rfile','wb');

fwrite (fid,A,'float32');

2. Read the file into a SIGNAL buffer. The following will read the floating point (/F) file

RFILE into T buffer 1, assigning a sample rate of 25000 Hz:

>R T 1 /B /F

Sample rate: 25000

Filename: RFILE

Exchanging spectrogram files between SIGNAL and MATLAB

Spectrogram exchange requires special attention because spectrograms are two-dimensional

objects and can be stored in multiple ways. The target program must know two things in

order to correctly unpack a spectrogram file: 1) whether the data is stored by rows or by

columns and 2) the actual dimensions of the spectrogram rows and columns.

Row-Column Order

MATLAB and SIGNAL write spectrogram files in the same order – ascending frequency at

the earliest time value, then ascending frequency at the next time value, and so on. Thus the

following spectrogram, consisting of 3 rows and 4 columns,

Freq | 9 10 11 12

| 5 6 7 8

| 1 2 3 4

-------------------

Time

will be written by both programs in the following order in the file RFILE

1 2 ... 24 25 26 27 28 29 30 31 32 33 34

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Engineering Design NIDisk Betriebsanweisung Seite 29