Differences

This shows you the differences between two versions of the page.

--- visual3d:documentation:pipeline:metric_commands:metric_compute_dft_coefficients [2024/06/19 12:51] – sgranger
+++ visual3d:documentation:pipeline:metric_commands:metric_compute_dft_coefficients [2025/06/20 20:09] (current) – wikisysop
@@ Line 1: / Line 1: @@
-{{the discrete fourier transform of a signal
+====== Metric Compute DFT Coefficients ======
-this command computes a metric signal containing the dft coefficients and the base frequency.
+The Discrete Fourier Transform of a Signal
-the form of the dft is as follows:
+This command computes a metric signal containing the DFT coefficients and the Base Frequency.
+The form of the DFT is as follows:
 p(t)= p0 + p1 sin(**w** t) + p2 cos(**w** t) + p3 sin(2**w** t) + p4 cos(2 **w** t) + ....
-where **w** = 2 * pi * base_frequency
+where **w** = 2 * PI * Base_Frequency
+The distinct difference between a DFT and an FFT is that the DFT allows the user the option to specify the base frequency.
+This is useful if you want to compare the coefficients across trials and/or across subjects. It also means that the base frequency has physical meaning, such as stride frequency.
-the distinct difference between a dft and an fft is that the dft allows the user the option to specify the base frequency.
+See also [[Visual3D:Documentation:Pipeline:Metric_Commands:Metric_Compute_Power_From_DFT_Coefficients|Compute Power from DFT coefficients]]
-this is useful if you want to compare the coefficients across trials and/or across subjects. it also means that the base frequency has physical meaning, such as stride frequency.
+{{:ComputeDFTdialog.jpg}}
-see also [[visual3d:documentation:pipeline:metric_commands:metric_compute_power_from_dft_coefficients|compute power from dft coefficients]]
+=== Pipeline Command ===
-computedftdialog.jpg
+<code>
+Metric_Compute_DFT_Coefficients
+/SIGNAL_TYPES=
+! /SIGNAL_NAMES=
+! /SIGNAL_FOLDER=ORIGINAL
+! /SIGNAL_COMPONENTS=ALL_COMPONENTS
+! /RESULT_SUFFIX=_DFT
+! /RESULT_FOLDER=DFT
+! /EVENT_SEQUENCE=
+! /EXCLUDE_EVENTS=
+! /START_FRAME=
+! /END_FRAME=
+! /USE_POINT_RATE=TRUE
+! /BASE_FREQUENCY=
+/NUM_FREQUENCIES=4
+;
+</code>
-==== pipeline command ====
+=== Signal_Components ===
-**metric_compute_dft_coefficients**
+Each component of the signal will generate a metric signal containing the coefficients for that component of the signal.
-/signal_types=
-! /signal_names=
-! /signal_folder=original
-! /signal_components=all_components
-! /result_suffix=_dft
-! /result_folder=dft
-!/[[visual3d:documentation:c3d_signal_types:event_label_data_type#event_sequence|event_sequence]]=
-!/[[visual3d:documentation:c3d_signal_types:event_label_data_type#exclude_events|exclude_events]]=
-! /start_frame=
-! /end_frame=
-! /use_point_rate=true
-! /base_frequency=
-/num_frequencies=4
-**;**
-==== signal_components ====
-each component of the signal will generate a metric signal containing the coefficients for that component of the signal.
+=== Number of Frequencies ===
-==== number of frequencies ====
+The parameter Num_Frequencies determines the number of coefficients that will be stored in the resulting metric signal.
-the parameter num_frequencies determines the number of coefficients that will be stored in the resulting metric signal.
+If Num_Frequencies is empty, the number is determined consistent with a standard DFT or FFT.
-if num_frequencies is empty, the number is determined consistent with a standard dft or fft.
+Num_Frequencies = 1 + NumFrames/2
-num_frequencies = 1 + numframes/2
+where the Maximum Number of Frequencies = 0.5*DataRate;
-where the maximum number of frequencies = 0.5*datarate;
+=== Event_Sequence ===
-==== event_sequence ====
+The [[Visual3D:Documentation:C3D_Signal_Types:EVENT_LABEL_Data_Type#Event_Sequence|Event Sequence and Exclude_Sequence]] define the range of frames used to compute the DFT coefficients
-the [[visual3d:documentation:c3d_signal_types:event_label_data_type#event_sequence|event sequence and exclude_sequence]] define the range of frames used to compute the dft coefficients
+=== Base_Frequency ===
-==== base_frequency ====
+If BASE_FREQUENCY is empty,
-if base_frequency is empty,
+Frequency= SamplingRate/NumberOfFrames (average per cycle per file)
+Else
-frequency= samplingrate/numberofframes (average per cycle per file)
+Frequency= Numerical value or Expression
-else
+=== Resulting Metric Signal ===
-frequency= numerical value or expression
+The metric signal is stored as follows (Base_Frequency, p0, p1, p2, p3, p4, ....)
-==== resulting metric signal ====
-the metric signal is stored as follows (base_frequency, p0, p1, p2, p3, p4, ....)
+The Base_Frequency and coefficients are stored as components of the signal.
-the base_frequency and coefficients are stored as components of the signal.
+If there are multiple ranges of data, there will be a "frame" or "row" for each range.
-if there are multiple ranges of data, there will be a "frame" or "row" for each range.
+see also : [[Visual3D:Documentation:Pipeline:Metric_Commands:Metric_Compute_Power_From_DFT_Coefficients|Metric_Compute_Power_From_DFT_Coefficients]]
-see also : [[visual3d:documentation:pipeline:metric_commands:metric_compute_power_from_dft_coefficients|metric_compute_power_from_dft_coefficients]]
-}}