pstack

Plot the stack of MultiAccum sample values for a specified pixel in an IR multiaccum image. Pixels from any of the SCI, ERR, DQ, or TIME image extensions can be plotted. The total number of samples is determined from the primary header keyword NSAMP and all samples (excluding the zeroth read) are plotted. The SCI, ERR, DQ, values are plotted as a function of sample time, while TIME values are plotted as a function of sample number. The sample times are read from the SAMPTIME keyword in the SCI header for each readout. If any of the ERR, DQ, SAMP, or TIME extensions have null data arrays, the value of the PIXVALUE extension header keyword is substituted for the pixel values. The plotted data values can be saved to an output text table or printed to the terminal.

The BUNIT keyword value is used to determine the starting units of the data, but you can plot either counts or rate using the optional keyword units.

../_images/pstack_example.png 
In [1]: xdata,ydata=pstack.pstack('ibh719grq_ima.fits',column=100,row=25,extname='sci')

The plotting data is returned as two arrays, to save them into variables issue the command as above:

In [1]: xdata
Out[2]:
array([ 100.651947,   93.470573,   86.2892  ,   79.107826,   71.926453,
         64.745079,   57.563702,   50.382328,   43.200954,   36.019581,
         28.838205,   21.65683 ,   14.475455,    7.29408 ,    0.112705,
          0.      ])

In [3]: ydata
Out[4]:
array([ 221.36606389,  219.5396653 ,  182.63100095,  169.178308  ,
        186.44084352,  158.3105126 ,  129.46997895,  129.92935701,
        106.14521852,   72.71721539,   69.68652119,   55.98828663,
         42.30755279,   13.12659422,   27.71404187,    0.        ])

Warning

Note that the arrays are structured in SCI order, so the final exposure is the first element in the array

Parameters

  • input [file]

    Input MultiAccum image name. This should be either a _ima or _raw file, containing all the data from multiple readouts. You must specify just the file name, with no extension designation.

  • col [integer]

    The column index of the pixel to be plotted.

  • row [integer]

    The row index of the pixel to be plotted.

  • extname = “sci” [string, allowed values: sci | err | dq | samp | time]

    Extension name (EXTNAME keyword value) of data to plot.

  • units = “counts” [string, allowed values: counts | rate]

    Plot “sci” or “err” data in units of counts or countrate (“rate”). Input data can be in either unit; conversion will be performed automatically. Ignored when plotting “dq”, “samp”, or “time” data.

  • title = “” [string]

    Title for the plot. If left blank, the name of the input image, appended with the extname and column and row being plotted, is used.

  • xlabel = “” [string]

    Label for the X-axis of the plot. If left blank, a suitable default is generated.

  • ylabel = “” [string]

    Label for the Y-axis of the plot. If left blank, a suitable default based on the plot units and the extname of the data is generated.

  • plot = True [bool] set plot to false if you only want the data returned

Usage

>>> python
>>> from wfc3tools import pstack
>>> xdata,ydata=pstack(inputFilename,column=x,row=y,extname="sci",units="counts|rate",title="",ylabel="",xlabel="")