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HDFView displays numerical datasets in a “spreadsheet”, which shows the data values in a grid. A one-dimensional dataset is displayed as a single column and a number of rows of dimension size. A two-dimensional dataset is displayed as a number of columns of the first dimension size and a number of rows of the second dimension size, i.e. dim[0]=height and dim[1]=width by default. You can change the order of the dimensions using the “Open As” command.

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Spreadsheet with a 2-D dataset


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subset
subset
5.2 Subset and Dimension Selection

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To make a selection, select a dataset from the tree and choose the “Open As” command from the Context menu. The selection dialog box appears. You can make a selection by dragging the mouse on the preview image or entering the values of start, end, and stride. The figure below shows that a subset of size 120 x 236 is selected from a true color image with the size of 533 x 533.

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The Dataset Selection dialog box

By default, a scalar dataset (e.g., a dataset or SDS of numbers) is displayed in a spreadsheet. You can also display a dataset as an image. To display a dataset as an image, click the Image radio button in the Dataset Selection dialog box and select a predefined color table for the dataset. This operation takes the data values of the dataset as values of an indexed array, i.e., as indices into a palette. The default palette will be used to create the image from the dataset if it does not have an attached palette. If the data values are not integers or have a range outside 0 to 255: they are binned into 256 equally spaced intervals.

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The "Open As" option allows you to set a range of valid data values, as well as setting specific values to be considered invalid, when displaying a dataset as an image (see dataset selection dialog figure above). By setting these, any pixels (data points) whose values are outside the valid range will not be shown and pixels whose value has been set as an invalid value will be mapped to 0. As an example, the figure below shows a dataset with the value '55' set to be invalid:

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5.2.2 Dimension Size

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2-D int array of size 8X9

111213141516171819
212223242526272829
313233343536373839
414243444546474849
515253545556575859
616263646566676869
717273747576777879
818283848586878889

The following are a few examples of subsets of the 2-D int array.

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The whole dataset -- start=(0, 0), end=(7, 8) and stride=(1, 1)

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Subset -- start=(2, 3), end=(6, 7) and stride=(1, 1)

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Subset with stride -- start=(2, 3), end=(5, 6) and stride=(2, 2)

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moredims
moredims
5.2.3 Three or More Dimensions

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The following figure shows how a 4-D integer dataset of size 5 x 4 x 3 x 2 is displayed. The data is displayed in a spreadsheet of 5 X 4 (dim0 by dim1), of page 2 (dim2), cutting locations 2 at dim3.

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Spreadsheet with 4-D dataset  

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swapdims
5.2.4 Swap Dimension and Data Transpose

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By default, the dataset is displayed as eight rows and nine columns.

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Default dimension order -- row index = dim[0], column index = dim[1]

Swap row and column dimensions to display the dataset as nine rows and eight columns. The order of data stays the same (counting from the location [0, 0], [0, 1], ... [2, 0], [2, 1], ...).

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Swap row/column dimensions -- row index = dim[1], column index = dim[0]

In some cases, we also want to transpose the data (changing the data order) when we swap the row and column dimensions. To transpose the data, select the “Transpose” option from the drop-down menu. For example, transpose the data to display the dataset as nine rows and eight columns. The order of the data is also changed.

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Transpose data -- row index = dim[1], column index = dim[0]

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5.2.5 Compound Dataset Options

HDFView displays HDF4 Vdata and a simple, one-dimension HDF5 compound dataset (without a nested compound) as a 2-D table with rows as records and columns as fields/members.

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Compound dataset

You can also select fields/members to display. For a contiguous selection, hold down the “Shift” key while clicking the first and last fields/members of your selection. For a discontiguous selection, hold down the “Ctrl” key while clicking the fields/members that you want to select.

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Field/Member selection of a compound dataset

HDFView displays a nested HDF5 compound dataset as a flat list of members. The nested names are separated by “.” (a period). For example, if a compound dataset “A” has the following nested structure:

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The flat list of members of the compound dataset “A” will be {a_name, b_name, c_name, nested_name->a_name, nested_name->c_name}}.

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Nested compound dataset

HDFView displays multi-dimension compound datasets as a 2-D table with nested sub-columns. The members are shown in the sub-columns.

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2-D compound dataset

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5.3 Display a Column/Row Line Plot

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The following figure shows that data of five columns are displayed in five lines of different colors. The horizontal labels are the row index of the 100 data points. The vertical labels are the ten points of equal data range with the maximum and minimum of the column data. The line legend is drawn at the right of the line plot with column names and line colors.

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Line plot

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5.4 Change Data Value

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Writing table data into an ASCII file is nearly transparent. Select “Export data to Text File” from the Table menu, and the Save Current Data to Text File dialog box pops up for you to enter the name of the file. The data values of the current table will be written to the file. The data values are separated by the data delimiter specified by the user options. The text file does not contain any datatype and dataspace information..

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Save current data to text file

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importtext
5.6 Import Data from a Text File

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A dataset can store object references of other datasets. You can open a dataset containing object references. You can then right click on any value in the dataset and it will give two options, to either open as a table or an image.

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Dataset storing object references

If opened as a table, then the dataset of reference value “7428” is opened as shown below.

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Dataset pointed by object reference

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5.7.2 Dataset Storing Dataset Region References

A dataset can store dataset region reference values. You can right click on any value to either show the dataset as a table or an image.

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Dataset pointed by region reference

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5.8 Save Data Values to a Binary File

The table data can be written to a binary file. Select “Export Data to Binary File” from the Table menu. Select the order in which you want the bytes to be. The Save Current Data to Binary File dialog box pops up for you to enter the name of the file. The data values of the current table will be written to the file. The binary file does not contain any datatype and dataspace information. Currently, only the entire contents of the table are written to a binary file..

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Save current data to binary file

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5.9 Import Data from a Binary File

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