# gdaWriteSome¶

## Purpose¶

Overwrites part of a variable in a GAUSS Data Archive.

## Format¶

retcode = gdaWriteSome(filename, x, varname, index)
Parameters:
• filename (string) – name of data file.
• x (matrix or array or string or string array) – data.
• varname (string) – variable name.
• index (scalar or Nx1 vector) – index into variable where new data is to be written.
Returns:

retcode (scalar) –

return code, 0 if successful, otherwise one of the following error codes:

 1 Null file name. 2 File open error. 3 File write error. 4 File read error. 5 Invalid data file type. 8 Variable not found. 10 File contains no variables. 14 File too large to be read on current platform. 15 Argument out of range. 17 Type mismatch. 18 Argument wrong size. 19 Data must be real. 20 Data must be complex.

## Examples¶

// Generate random variable x
x = rndn(100, 50);

// Create GDA myFile
retcode1 = gdaCreate("myfile.gda", 1);

// Write x  to myfile as x1
retcode2 = gdaWrite("myfile.gda", x, "x1");

// Generate random variable y
y = rndn(75, 5);

// Define index
index = { 52, 4 };

// Overwrites part of x1
retcode3 = gdaWriteSome("myfile.gda", y, "x1", index);


This example replaces $$75 * 5= 375$$ elements in x1, beginning with the $$[52, 4]$$ element, with the elements in y.

## Remarks¶

This command overwrites part of the variable varname in filename with the data contained in x. The new data is written to varname beginning at the position indicated by index.

If index is a scalar, it will be interpreted as the indexth element of the variable. Thus if varname references a 10x5 matrix, an index of 42 would indicate the 42nd element, which is equivalent to the $$[8,2]$$ element of the matrix (remember that GAUSS matrices are stored in row major order). If index is an Nx1 vector, then N must equal the number of dimensions in the variable referenced by varname.

If varname references a string, then index must be a scalar containing an index into the string in characters.

gdaWriteSome() may not be used to extend the size of a variable in a GDA. If there are more elements (or characters for strings) in x than there are from the indexed position of the specified variable to the end of that variable, then gdaWriteSome() will fail. Call gdaAppend() to append data to an existing variable.

The shape of x need not match the shape of the variable referenced by varname. If varnum references an NxK matrix, then x may be any LxM matrix (or P-dimensional array) that satisfies the size limitations described above. If x contains R elements, then the elements in x will simply replace the indexed element of the specified variable and the subsequent R-1 elements (as they are laid out in memory).

If varname references a string array, then the size of the overall variable will change if the sum of the length of the string array elements in x is different than the sum of the length of the elements that they are replacing.

In this case, if the variable increases in size, then the variable data will be rewritten after the last variable in the data file, moving the variable descriptor table to make room for the data and leaving empty bytes in its old location. This does not change the index of the variable because variable indices are determined NOT by the order of the variable data in a GDA, but by the order of the variable descriptors. If the variable decreases in size, then gdaWriteSome() leaves empty bytes between the end of the variable and the beginning of the next variable in the data file. Call gdaPack() to pack the data in a GDA, so it contains no empty bytes.