Extracting special parts of a matrix function
nils Frank
Hello everyone,
I have a function in the first row of a result matrix, and also in the second.
I'm separating the first row to write only the parts of it into a new matrix, for example, a multiplication by the second derivative of phi1.
Unfortunately, there's no result, just square brackets. Can anyone help? Thanks in advance.
Sympy Code:
#Testmatrix
C = d*sp.diff(phi1(t), t)+l*m*(2*g*sp.sin(phi1(t))+l*sp.sin(phi1(t)-phi2(t))*(sp.diff(phi2(t), t))**2+ l*sp.cos(phi1(t)-phi2(t))*sp.diff(phi2(t), t,t)+ 2*l*sp.diff(phi1(t), t,t))
D = sp.diff(phi2(t), t) + sp.diff(phi1(t), t)
Bw_Lag_Q_Test = sp.Matrix([[C], [D]])
Bw_Lag_Q_Test
erste_reihe_BW_Test = Bw_Lag_Q_Test.row(0)
erste_reihe_BW_Test
# Extract parts of erste_reihe_BW_Test
erste_reihe_BW_Test = Bw_Lag_Q_Test.row(0)
Extract_0 = [term.coeff(sp.diff(phi1(t), t,t)) for term in erste_reihe_BW if term.has(sp.diff(phi1(t), t,t))]
Extract_0
thomas...@gmail.com
Could it be that this is not a matrix, but just an expression that requires multiple lines to display?
Tom
(Dr. Thomas S. Ligon)
Frohnloher Str. 6a
81475 Muenchen
Germany
Tel. +49(89)74575075
From: 'nils Frank' via sympy <sy...@googlegroups.com>
Sent: Wednesday, March 12, 2025 9:51 AM
To: sympy <sy...@googlegroups.com>
Subject: [sympy] Extracting special parts of a matrix function
Hello everyone,
Hello everyone,
I have a function in the first row of a result matrix, and also in the second.
I'm separating the first row to write only the parts of it into a new matrix, for example, a multiplication by the second derivative of phi1.
Unfortunately, there's no result, just square brackets. Can anyone help? Thanks in advance.
Sympy Code:
#Testmatrix
C = d*sp.diff(phi1(t), t)+l*m*(2*g*sp.sin(phi1(t))+l*sp.sin(phi1(t)-phi2(t))*(sp.diff(phi2(t), t))**2+ l*sp.cos(phi1(t)-phi2(t))*sp.diff(phi2(t), t,t)+ 2*l*sp.diff(phi1(t), t,t))
D = sp.diff(phi2(t), t) + sp.diff(phi1(t), t)
Bw_Lag_Q_Test = sp.Matrix([[C], [D]])
Bw_Lag_Q_Test
erste_reihe_BW_Test = Bw_Lag_Q_Test.row(0)
erste_reihe_BW_Test
# Extract parts of erste_reihe_BW_Test
erste_reihe_BW_Test = Bw_Lag_Q_Test.row(0)
Extract_0 = [term.coeff(sp.diff(phi1(t), t,t)) for term in erste_reihe_BW if term.has(sp.diff(phi1(t), t,t))]
Extract_0
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