Select certain terms in an expression
4
I would like to have a function to select terms containing q[i] terms in expressions, for example, for an expression
a q[i]+b +c q[j]+d
I would like the function to return
a q[i]+c q[j]
as result. Also at the same time, for a bare
q[i]
the same function would return
q[i]
How to realize such function? Thanks
pattern-matching filtering
asked yesterday
XiaoaiXXiaoaiX
1105
add a comment |
4
I would like to have a function to select terms containing q[i] terms in expressions, for example, for an expression
a q[i]+b +c q[j]+d
I would like the function to return
a q[i]+c q[j]
as result. Also at the same time, for a bare
q[i]
the same function would return
q[i]
How to realize such function? Thanks
pattern-matching filtering
asked yesterday
XiaoaiXXiaoaiX
1105
add a comment |
4
4
4
I would like to have a function to select terms containing q[i] terms in expressions, for example, for an expression
a q[i]+b +c q[j]+d
I would like the function to return
a q[i]+c q[j]
as result. Also at the same time, for a bare
q[i]
the same function would return
q[i]
How to realize such function? Thanks
pattern-matching filtering
asked yesterday
XiaoaiXXiaoaiX
1105
I would like to have a function to select terms containing q[i] terms in expressions, for example, for an expression
a q[i]+b +c q[j]+d
I would like the function to return
a q[i]+c q[j]
as result. Also at the same time, for a bare
q[i]
the same function would return
q[i]
How to realize such function? Thanks
pattern-matching filtering
pattern-matching filtering
asked yesterday
XiaoaiXXiaoaiX
1105
asked yesterday
XiaoaiXXiaoaiX
1105
edited yesterday
XiaoaiX
asked yesterday
XiaoaiXXiaoaiX
1105
asked yesterday
XiaoaiXXiaoaiX
1105
asked yesterday
XiaoaiXXiaoaiX
1105
1105
add a comment |
add a comment |
2 Answers
2
active
oldest
votes
3
expr = a q[i] + b + c q[j] + d;
f = DeleteCases[#, Except[_. _q], If[Head[#] === q, 0, 1]] &
f @ expr
a q[i] + c q[j]
f @ q[i]
q[i]
Alternatively,
f2 = Select[#, Function[x, If[Head@# === q, True, Not @ FreeQ[x, _q]]]] &;
f2 @ expr
a q[i] + c q[j]
f2 @ q[i]
q[i]
answered yesterday
kglrkglr
178k9198409
This realize the first requirement, but for the bare $q[i]$, it returns $q$
– XiaoaiX
yesterday
@XiaoaiX, I will update if i find a fix.
– kglr
yesterday
thanks, from your answer, I also got confused about how the Select and Cases handle the List argument, see the question I just post here mathematica.stackexchange.com/questions/189270/…
– XiaoaiX
yesterday
add a comment |
3
A pattern-based approach.
fn[x_. y_q + z_.] := x y + fn[z]
_fn = 0;
a q[i] + b + c q[j] + d // fn
q[i] // fn
a q[i] + c q[j]
q[i]
answered yesterday
Mr.Wizard♦Mr.Wizard
230k294741040
add a comment |
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2 Answers
2
active
oldest
votes
2 Answers
2
active
oldest
votes
active
oldest
votes
active
oldest
votes
3
expr = a q[i] + b + c q[j] + d;
f = DeleteCases[#, Except[_. _q], If[Head[#] === q, 0, 1]] &
f @ expr
a q[i] + c q[j]
f @ q[i]
q[i]
Alternatively,
f2 = Select[#, Function[x, If[Head@# === q, True, Not @ FreeQ[x, _q]]]] &;
f2 @ expr
a q[i] + c q[j]
f2 @ q[i]
q[i]
answered yesterday
kglrkglr
178k9198409
This realize the first requirement, but for the bare $q[i]$, it returns $q$
– XiaoaiX
yesterday
@XiaoaiX, I will update if i find a fix.
– kglr
yesterday
thanks, from your answer, I also got confused about how the Select and Cases handle the List argument, see the question I just post here mathematica.stackexchange.com/questions/189270/…
– XiaoaiX
yesterday
add a comment |
3
expr = a q[i] + b + c q[j] + d;
f = DeleteCases[#, Except[_. _q], If[Head[#] === q, 0, 1]] &
f @ expr
a q[i] + c q[j]
f @ q[i]
q[i]
Alternatively,
f2 = Select[#, Function[x, If[Head@# === q, True, Not @ FreeQ[x, _q]]]] &;
f2 @ expr
a q[i] + c q[j]
f2 @ q[i]
q[i]
answered yesterday
kglrkglr
178k9198409
This realize the first requirement, but for the bare $q[i]$, it returns $q$
– XiaoaiX
yesterday
@XiaoaiX, I will update if i find a fix.
– kglr
yesterday
thanks, from your answer, I also got confused about how the Select and Cases handle the List argument, see the question I just post here mathematica.stackexchange.com/questions/189270/…
– XiaoaiX
yesterday
add a comment |
3
3
3
expr = a q[i] + b + c q[j] + d;
f = DeleteCases[#, Except[_. _q], If[Head[#] === q, 0, 1]] &
f @ expr
a q[i] + c q[j]
f @ q[i]
q[i]
Alternatively,
f2 = Select[#, Function[x, If[Head@# === q, True, Not @ FreeQ[x, _q]]]] &;
f2 @ expr
a q[i] + c q[j]
f2 @ q[i]
q[i]
answered yesterday
kglrkglr
178k9198409
expr = a q[i] + b + c q[j] + d;
f = DeleteCases[#, Except[_. _q], If[Head[#] === q, 0, 1]] &
f @ expr
a q[i] + c q[j]
f @ q[i]
q[i]
Alternatively,
f2 = Select[#, Function[x, If[Head@# === q, True, Not @ FreeQ[x, _q]]]] &;
f2 @ expr
a q[i] + c q[j]
f2 @ q[i]
q[i]
answered yesterday
kglrkglr
178k9198409
edited yesterday
answered yesterday
kglrkglr
178k9198409
answered yesterday
kglrkglr
178k9198409
answered yesterday
kglrkglr
178k9198409
178k9198409
This realize the first requirement, but for the bare $q[i]$, it returns $q$
– XiaoaiX
yesterday
@XiaoaiX, I will update if i find a fix.
– kglr
yesterday
thanks, from your answer, I also got confused about how the Select and Cases handle the List argument, see the question I just post here mathematica.stackexchange.com/questions/189270/…
– XiaoaiX
yesterday
add a comment |
This realize the first requirement, but for the bare $q[i]$, it returns $q$
– XiaoaiX
yesterday
@XiaoaiX, I will update if i find a fix.
– kglr
yesterday
thanks, from your answer, I also got confused about how the Select and Cases handle the List argument, see the question I just post here mathematica.stackexchange.com/questions/189270/…
– XiaoaiX
yesterday
This realize the first requirement, but for the bare $q[i]$, it returns $q$
– XiaoaiX
yesterday
This realize the first requirement, but for the bare $q[i]$, it returns $q$
– XiaoaiX
yesterday
@XiaoaiX, I will update if i find a fix.
– kglr
yesterday
@XiaoaiX, I will update if i find a fix.
– kglr
yesterday
thanks, from your answer, I also got confused about how the Select and Cases handle the List argument, see the question I just post here mathematica.stackexchange.com/questions/189270/…
– XiaoaiX
yesterday
thanks, from your answer, I also got confused about how the Select and Cases handle the List argument, see the question I just post here mathematica.stackexchange.com/questions/189270/…
– XiaoaiX
yesterday
add a comment |
3
A pattern-based approach.
fn[x_. y_q + z_.] := x y + fn[z]
_fn = 0;
a q[i] + b + c q[j] + d // fn
q[i] // fn
a q[i] + c q[j]
q[i]
answered yesterday
Mr.Wizard♦Mr.Wizard
230k294741040
add a comment |
3
A pattern-based approach.
fn[x_. y_q + z_.] := x y + fn[z]
_fn = 0;
a q[i] + b + c q[j] + d // fn
q[i] // fn
a q[i] + c q[j]
q[i]
answered yesterday
Mr.Wizard♦Mr.Wizard
230k294741040
add a comment |
3
3
3
A pattern-based approach.
fn[x_. y_q + z_.] := x y + fn[z]
_fn = 0;
a q[i] + b + c q[j] + d // fn
q[i] // fn
a q[i] + c q[j]
q[i]
answered yesterday
Mr.Wizard♦Mr.Wizard
230k294741040
A pattern-based approach.
fn[x_. y_q + z_.] := x y + fn[z]
_fn = 0;
a q[i] + b + c q[j] + d // fn
q[i] // fn
a q[i] + c q[j]
q[i]
answered yesterday
Mr.Wizard♦Mr.Wizard
230k294741040
answered yesterday
Mr.Wizard♦Mr.Wizard
230k294741040
answered yesterday
Mr.Wizard♦Mr.Wizard
230k294741040
answered yesterday
Mr.Wizard♦Mr.Wizard
230k294741040
230k294741040
add a comment |
add a comment |
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