Reading Raw Files

The RawRead class is used to (surprise…) read .RAW-files. The file to read is given as parameter when creating the RawRead object. The object wil read the file and construct a structure of objects which can be used to access the data inside the .RAW-file. All traces on the .RAW-file are uploaded into memory.

See RAW File Structure for details of the contents of a .RAW-file.

The .RAW-file contains different traces for voltages and currents in the simulation.

Typically (for a transient analysis), a trace contain a value (voltage/current) for each different time point in the simulation. There is a list of time values, and a separate list of trace values for each trace. So each trace uses the same time values. If there were different steps (e.g. for a DC sweep), then there is a set of lists with time/value data for each step.

Note that for an AC analysis, the traces are frequency-versus-value instead of time-versus-value. We will use ‘time’ as an example further in this text.

The RawRead class has all the methods that allow the user to access the X-axis and trace values. If there is any stepped data (.STEP primitives), the RawRead class will try to load the log information from the same directory as the raw file in order to obtain the STEP information.

You can get a list of all trace names using the get_trace_names() method.

Use method get_trace() to get the trace data, which consists of values for 1 or more simulation steps. It will return a PyLTSpice.raw_classes.Trace object. Use this object’s get_wave() method to get the actual data points for a step.

Use the method get_axis() to get the ‘time’ data. If there were multiple steps in the simulation, specify the number for which step you want to retrieve the time data.

Now that you have lists with the times and corresponding values, you can plot this information in an X/Y plot.

Note that all the data will be returned as numpy arrays.

See the class documentation for more details :

• PyLTSpice.raw_read.RawRead

• PyLTSpice.raw_classes.Trace

Example

The example below demonstrates the usage of the RawRead class. It reads a .RAW file and uses the matplotlib library to plot the results of two traces in a separate subplots.

from PyLTSpice import RawRead
import matplotlib.pyplot as plt         # use matplotlib for plotting the results

raw = RawRead("some_random_file.raw")   # Read the RAW file contents from disk

print(raw.get_trace_names())            # Get and print a list of all the traces
print(raw.get_raw_property())           # Print all the properties found in the Header section

vin = raw.get_trace('V(in)')            # Get the trace data
vout = raw.get_trace('V(out)')          # Get the second trace

steps = raw.get_steps()                 # Get list of step numbers ([0,1,2]) for sweeped simulations
                                        # Returns [0] if there is just 1 step

plt.figure()                            # Create the canvas for plotting

_, (ax1, ax2) = plt.subplots(2, 1, sharex=True)  # Create two subplots

for ax in (ax1, ax2):                   # Use grid on both subplots
    ax.grid(True)

plt.xlim([0.9e-3, 1.2e-3])              # Limit the X axis to just a subrange

xdata = raw.get_axis()                  # Get the X-axis data (time)

ydata = vin.get_wave()                  # Get all the values for the 'vin' trace
ax1.plot(xdata, ydata)                  # Do an X/Y plot on first subplot

ydata = vout.get_wave()                 # Get all the values for the 'vout' trace
ax1.plot(xdata, ydata)                  # Do an X/Y plot on first subplot as well

for step in steps:                      # On the second plot, print all the STEPS of Vout
    ydata = vout.get_wave(step)         # Retrieve the values for this step
    xdata = raw.get_axis(step)          # Retrieve the time vector
    ax2.plot(xdata, ydata)              # Do X/Y plot on second subplot

plt.show()                              # Show matplotlib's interactive window with the plots