Index Go backward to 3.1.1 An example Go up to 3.1 The Archive File Go forward to 3.1.3 Another example

3.1.2 Getrectg function variables

A few variables aren't used by the OPeNDAP Matlab GUI, but are used by getrectg, the getxxx function used here. They are documented here because the getrectg function is flexible enough to be used for many different gridded datasets. See section 3.2 for more information about the getxxx API.

Server

The server from which the data in question will come.

axes_order

The dataset may store its variables in a different order than the OPeNDAP Matlab GUI expects them. You can use this vector to rearrange the variables before getrectg returns them.

Time_Offset

Data providers often disagree whether a time value marks the beginning of the interval, or the middle, and whether the first unit is number one or number zero. You can use this six-element vector to provide a constant with which to adjust the time values from the dataset. The elements are adjustments to the year, month, day, hour, minute, and second, in that order. For example, the offset vector in the example instructs getrectg to subtract one day from the day values in the dataset before returning them to the OPeNDAP Matlab GUI.

LongitudeName, LatitudeName, TimeName, DepthName

These identify the names of the spatial quantities as used in the dataset. Data requests to the OPeNDAP server will be made with these names. The variables may contain empty strings if no meaningful information is returned by the server about any of these variables.

SelectableVariables

The names of the variables in the dataset. These are the names that will be used in displaying the data to a user. Wherever possible, you should use a name that is already in use in the browser. For example, `Salinity' is already in use. If you are adding a dataset containing salinity measurements, don't call it `Salt', unless there is some reason you don't want to see your dataset in a list of datasets containing salinity measurements.

DodsName

This is the name of the selectable variable as used by the dataset server. Data requests to the dataset server will be made using these names. For example, though the OPeNDAP standard is to use `Salinity' (see above), the dataset server itself uses `SALT', and requests to that server must be made with that name. Each entry on this list must exactly correspond to an entry on the SelectableVariables list.

DataNull

This is a vector of null values, indicating the "no data" value for each of the spatial variables (in order: Time, Longitude, Latitude, and Depth), and each of the selectable variables (in the same order as the SelectableVariables list. As data from the remote dataset is interned into Matlab, any values matching the appropriate element of this array will be changed into the Matlab NaN ("not a number") value.

DataScale

A 2-column array, to be used in a linear conversion from the data as it is received from the remote dataset. The first column is the intercept and the second the slope. The rows the array correspond to the entries in the DataNull array. Entries of [NaN NaN] or [0 1] do no scaling. Within the OPeNDAP Matlab GUI an effort is made to present the data to the user in SI units. For example, density would be presented in kg/m³. Not required.

NOTE: While technically not required, DataScale and DataNull are in practice almost essential for the return of intelligible results to the user. In addition, for datasets that use extreme values as a bad or missing data flag, (e.g., -9e42) , no meaningful plotting will be able to be done within the browser unless DataNull is declared.