Open e4c2077a-2707-419a-892c-dfa2c4822290 opened 13 years ago
Description changed:
---
+++
@@ -8,7 +8,10 @@
def pulse(tonset, tdur, amp):
- """ returns a square pulse as a function of x, f(x) the pulse is defined as follows: tonset -- start of pulse tdur -- duration of pulse amp -- amplitude of pulse """
+ """ returns a square pulse as a function of x, f(x) the pulse is defined as follows: t
+ onset -- start of pulse
+ tdur -- duration of pulse
+ amp -- amplitude of pulse """
f(x)= amp*(sign(x-tonset)/2-sign(x-tonset-tdur)/2)
@@ -30,7 +33,7 @@
*TypeError: unable to make sense of Maxima expression 'v(x)=-(2*(at(integrate(signum(x-5)-signum(x-13),x),[x=0,v(x)=0]))-2*int\ egrate(signum(x-5)-signum(x-13),x)-x^2)/2' in Sage^*
-desolve_laplace leads to similar error:
+desolve_laplace leads to similar error:
sage: desolve(de=dvdx, ivar=x, dvar=v, ics=[0,0])
Description changed:
---
+++
@@ -8,10 +8,7 @@
def pulse(tonset, tdur, amp):
- """ returns a square pulse as a function of x, f(x) the pulse is defined as follows: t
- onset -- start of pulse
- tdur -- duration of pulse
- amp -- amplitude of pulse """
+ """ returns a square pulse as a function of x, f(x) the pulse is defined as follows: t onset -- start of pulse tdur -- duration of pulse amp -- amplitude of pulse """
f(x)= amp*(sign(x-tonset)/2-sign(x-tonset-tdur)/2)
@@ -41,4 +38,12 @@
According to Nils Bruin, the problem is that Maxima 'at' function. As described in Ticket #385, this can be a problem with the implementation of 'at' for SR.
+Strange enough, when using other functions, the solver works nicely
+
+sage: dvdx = diff(v, x)-x -sin(x) == 0
+
+sage: desolve(de=dvdx, ivar=x, dvar=v, ics=[http://trac.sagemath.org/sage_trac/log/?revs=0 "[0,0]"])
+
+now Sage returns 1/2*x!^2 - cos(x) + 1
+
Detailed information (and a real example) can be found here: http://groups.google.com/group/sage-support/browse_thread/thread/8cc67d39510faca2
Changed keywords from none to maxima, at, desolve
Description changed:
---
+++
@@ -1,49 +1,54 @@
When trying to solve a simple ODE whose rhs contains a function, Sage fails to interpret the Maxima output.
-Here a minimal example is #========================================================================= sage: x=var('x') # independent variable
+Here a minimal example is
+```
+#=====================
+sage: x=var('x') # independent variable
sage: v=function('v', x) # dependent variable
-\# we define a custom square pulse function
-
+# we define a custom square pulse function
def pulse(tonset, tdur, amp):
-
- """ returns a square pulse as a function of x, f(x) the pulse is defined as follows: t onset -- start of pulse tdur -- duration of pulse amp -- amplitude of pulse """
-
+"""
+returns a square pulse as a function of x, f(x)
+the pulse is defined as follows:
+t onset -- start of pulse
+tdur -- duration of pulse
+amp -- amplitude of pulse
+"""
f(x)= amp*(sign(x-tonset)/2-sign(x-tonset-tdur)/2)
-
return f
-\# create my pulse function
-
+# create my pulse function
sage: mypulse = pulse(tonset=5, tdur=5, amp=2)
-\# define differential equation s
-
+# define differential equation s
sage: dvdx = diff(v, x)-x -mypulse == 0 # mypulse(x) is function
-\# get the evolution of v
-
+# get the evolution of v
myvolt = desolve(de=dvdx, ivar=x, dvar=v, ics=[0,0])
-#========================================================================= The error message is:
+#=======
+The error message is:
-*TypeError: unable to make sense of Maxima expression 'v(x)=-(2*(at(integrate(signum(x-5)-signum(x-13),x),[x=0,v(x)=0]))-2*int\ egrate(signum(x-5)-signum(x-13),x)-x^2)/2' in Sage^*
-
+''TypeError: unable to make sense of Maxima expression 'v(x)=-(2*(at(integrate(signum(x-5)-signum(x-13),x),[x=0,v(x)=0]))-2*int\ egrate(signum(x-5)-signum(x-13),x)-x^2)/2' in Sage^''
+```
desolve_laplace leads to similar error:
+```
sage: desolve(de=dvdx, ivar=x, dvar=v, ics=[0,0])
-*TypeError: unable to make sense of Maxima expression 'ilt(((laplace(signum(x-5),x,?g2733)-laplace(signum(x-13),x,?g2733)+v(0)\ )*?g2733<sup>2+1)/?g2733</sup>3,?g2733,x)' in Sage*
-
+''TypeError: unable to make sense of Maxima expression 'ilt(((laplace(signum(x-5),x,?g2733)-laplace(signum(x-13),x,?g2733)+v(0)\ )*?g2733^2+1)/?g2733^3,?g2733,x)' in Sage''
+```
According to Nils Bruin, the problem is that Maxima 'at' function. As described in Ticket #385, this can be a problem with the implementation of 'at' for SR.
Strange enough, when using other functions, the solver works nicely
+```
sage: dvdx = diff(v, x)-x -sin(x) == 0
sage: desolve(de=dvdx, ivar=x, dvar=v, ics=[http://trac.sagemath.org/sage_trac/log/?revs=0 "[0,0]"])
-
+```
now Sage returns 1/2*x!^2 - cos(x) + 1
Detailed information (and a real example) can be found here: http://groups.google.com/group/sage-support/browse_thread/thread/8cc67d39510faca2
Thanks, Jose! Just a few pointers:
Changed author from JGuzman to none
As to the ticket, see the sage-support thread in question. The essential problem is that in laplace
and taylor
we take the answer from Maxima and send it to SR, which does parse the at
correctly via the Maxima string thingie in calculus/calculus.py, but in the desolve_*
functions we just coerce to .sage()
, which does not. Probably changing this would fix it.
Description changed:
---
+++
@@ -1,54 +1,66 @@
When trying to solve a simple ODE whose rhs contains a function, Sage fails to interpret the Maxima output.
-Here a minimal example is
+Here a minimal example is
-#===================== sage: x=var('x') # independent variable sage: v=function('v', x) # dependent variable +```
-# we define a custom square pulse function
+# we define a custom square pulse function
+
+```
def pulse(tonset, tdur, amp):
"""
-returns a square pulse as a function of x, f(x)
-the pulse is defined as follows:
-t onset -- start of pulse
-tdur -- duration of pulse
-amp -- amplitude of pulse
-"""
-# create my pulse function
+now we create a pulse function
+
+ sage: mypulse = pulse(tonset=5, tdur=5, amp=2) +
+and define differential equation
-# define differential equation s
+ sage: dvdx = diff(v, x)-x -mypulse == 0 # mypulse(x) is function +
-# get the evolution of v
+To get the evolution of v we can use desolve
+
+ myvolt = desolve(de=dvdx, ivar=x, dvar=v, ics=[0,0]) +
-#======= + The error message is:
-''TypeError: unable to make sense of Maxima expression 'v(x)=-(2(at(integrate(signum(x-5)-signum(x-13),x),[x=0,v(x)=0]))-2int\ egrate(signum(x-5)-signum(x-13),x)-x^2)/2' in Sage^'' -``` +TypeError: unable to make sense of Maxima expression 'v(x)=-(2(at(integrate(signum(x-5)-signum(x-13),x),[x=0,v(x)=0]))-2int\ egrate(signum(x-5)-signum(x-13),x)-x^2)/2' in Sage^ + desolve_laplace leads to similar error:
sage: desolve(de=dvdx, ivar=x, dvar=v, ics=[0,0])
+```
-''TypeError: unable to make sense of Maxima expression 'ilt(((laplace(signum(x-5),x,?g2733)-laplace(signum(x-13),x,?g2733)+v(0)\ )*?g2733^2+1)/?g2733^3,?g2733,x)' in Sage''
-```
+*TypeError: unable to make sense of Maxima expression 'ilt(((laplace(signum(x-5),x,?g2733)-laplace(signum(x-13),x,?g2733)+v(0)\ )*?g2733<sup>2+1)/?g2733</sup>3,?g2733,x)' in Sage*
+
According to Nils Bruin, the problem is that Maxima 'at' function. As described in Ticket #385, this can be a problem with the implementation of 'at' for SR.
Strange enough, when using other functions, the solver works nicely
sage: dvdx = diff(v, x)-x -sin(x) == 0 +sage: desolve(de=dvdx, ivar=x, dvar=v, ics=[0,0]"]) +```
-sage: desolve(de=dvdx, ivar=x, dvar=v, ics=[http://trac.sagemath.org/sage_trac/log/?revs=0 "[0,0]"]) -``` now Sage returns 1/2*x!^2 - cos(x) + 1
Detailed information (and a real example) can be found here: http://groups.google.com/group/sage-support/browse_thread/thread/8cc67d39510faca2
I re-formatted the text according to kcrisman (thanks a lot for the suggestion!). I will have a look to the code soon. I am looking forward to implement it. If I understood correctly, the only thing to do is to make desolve_* take the answer from Maxima to SR.
I changed the summary to delimit the error more carefully. Additional, a more detailed explanation is given of cases in which Sage is able to interpret Maxima output. I guess, the problem is that Sage is not able to interpret the integration limits prompted by the maxima expression.
Description changed:
---
+++
@@ -1,48 +1,46 @@
-When trying to solve a simple ODE whose rhs contains a function, Sage fails to interpret the Maxima output.
+When trying to solve a simple ODE whose rhs contains a function, Sage fails to interpret the Maxima output if this contains integration limits.
-Here a minimal example is
+## A minimal example
sage: x=var('x') # independent variable sage: v=function('v', x) # dependent variable
+if we now define a custom square pulse function
-\# we define a custom square pulse function
-
-```
+```python
def pulse(tonset, tdur, amp):
-"""
+ """
returns a square pulse as a function of x, f(x)
the pulse is defined as follows:
t onset -- start of pulse
tdur -- duration of pulse
amp -- amplitude of pulse
"""
+
f(x)= amp*(sign(x-tonset)/2-sign(x-tonset-tdur)/2)
return f
- now we create a pulse function
sage: mypulse = pulse(tonset=5, tdur=5, amp=2)
-and define differential equation +and define differential equation
sage: dvdx = diff(v, x)-x -mypulse == 0 # mypulse(x) is function
- To get the evolution of v we can use desolve
myvolt = desolve(de=dvdx, ivar=x, dvar=v, ics=[0,0])
The error message is:
-TypeError: unable to make sense of Maxima expression 'v(x)=-(2(at(integrate(signum(x-5)-signum(x-13),x),[x=0,v(x)=0]))-2int\ egrate(signum(x-5)-signum(x-13),x)-x^2)/2' in Sage^
+python +TypeError: unable to make sense of Maxima expression 'v(x)=-(2*(at(integrate(signum(x-5)-signum(x-13),x),[x=0,v(x)=0]))-2*int\egrate(signum(x-5)-signum(x-13),x)-x^2)/2' in Sage^ +
desolve_laplace leads to similar error:
@@ -50,17 +48,34 @@ sage: desolve(de=dvdx, ivar=x, dvar=v, ics=[0,0])
-*TypeError: unable to make sense of Maxima expression 'ilt(((laplace(signum(x-5),x,?g2733)-laplace(signum(x-13),x,?g2733)+v(0)\ )*?g2733<sup>2+1)/?g2733</sup>3,?g2733,x)' in Sage*
+```python
+TypeError: unable to make sense of Maxima expression 'ilt(((laplace(signum(x-5),x,?g2733)-laplace(signum(x-13),x,?g2733)+v(0)\ )*?g2733^2+1)/?g2733^3,?g2733,x)' in Sage
+```
According to Nils Bruin, the problem is that Maxima 'at' function. As described in Ticket #385, this can be a problem with the implementation of 'at' for SR.
-Strange enough, when using other functions, the solver works nicely
+## Expressions that work
+And adding the **sign** function to the differential function does not affect the solution.
-sage: dvdx = diff(v, x)-x -sin(x) == 0 +sage: dvdx = diff(v, x)-v -sign(x) == 0 sage: desolve(de=dvdx, ivar=x, dvar=v, ics=[0,0]"]) +sage: (c + integrate(e^(-x)sgn(x), x))e^x
-now Sage returns 1/2*x!^2 - cos(x) + 1
+However, adding initial conditions produces an output that Sage is not able to evaluate
-Detailed information (and a real example) can be found here: http://groups.google.com/group/sage-support/browse_thread/thread/8cc67d39510faca2
+```
+sage: desolve(de = dvdx, ivar=x, dvar=v, ics=[0,0])
+```
+
+The output is:
+
+```python
+TypeError: unable to make sense of Maxima expression 'v(x)=e^x*integrate(e^-x*signum(x),x)-e^x*(at(integrate(e^-x*signum(x),x),[x=0,v(x)=0]))' in Sage
+
+```
+
+I guess Sage is not able to interpret the integrations limits prompted by Maxima (e.g [t=0,v(t)=0]).
+
+Detailed information (and a more realistic example) can be found here: http://groups.google.com/group/sage-support/browse_thread/thread/8cc67d39510faca2
Description changed:
---
+++
@@ -39,7 +39,10 @@
The error message is:
```python
-TypeError: unable to make sense of Maxima expression 'v(x)=-(2*(at(integrate(signum(x-5)-signum(x-13),x),[x=0,v(x)=0]))-2*int\egrate(signum(x-5)-signum(x-13),x)-x^2)/2' in Sage^
+TypeError:
+unable to make sense of Maxima expression
+'v(x)=-(2*(at(integrate(signum(x-5)-signum(x-13),x),[x=0,v(x)=0]))-2*int\egrate(signum(x-5)-signum(x-13),x)-x^2)/2'
+in Sage
desolve_laplace leads to similar error: @@ -49,7 +52,10 @@
```python
-TypeError: unable to make sense of Maxima expression 'ilt(((laplace(signum(x-5),x,?g2733)-laplace(signum(x-13),x,?g2733)+v(0)\ )*?g2733^2+1)/?g2733^3,?g2733,x)' in Sage
+TypeError:
+unable to make sense of Maxima expression
+'ilt(((laplace(signum(x-5),x,?g2733)-laplace(signum(x-13),x,?g2733)+v(0)\ )*?g2733^2+1)/?g2733^3,?g2733,x)'
+in Sage
According to Nils Bruin, the problem is that Maxima 'at' function. As described in Ticket #385, this can be a problem with the implementation of 'at' for SR. @@ -72,7 +78,10 @@ The output is:
-TypeError: unable to make sense of Maxima expression 'v(x)=e^x*integrate(e^-x*signum(x),x)-e^x*(at(integrate(e^-x*signum(x),x),[x=0,v(x)=0]))' in Sage
+TypeError:
+unable to make sense of Maxima expression
+'v(x)=e^x*integrate(e^-x*signum(x),x)-e^x*(at(integrate(e^-x*signum(x),x),[x=0,v(x)=0]))'
+ in Sage
Change owner to burcin (I do not know why it changed last time !), and change the typesetting of TypeError
Description changed:
---
+++
@@ -65,7 +65,7 @@
sage: dvdx = diff(v, x)-v -sign(x) == 0 -sage: desolve(de=dvdx, ivar=x, dvar=v, ics=[0,0]"]) +sage: desolve(de=dvdx, ivar=x, dvar=v"]) sage: (c + integrate(e^(-x)sgn(x), x))e^x
Description changed:
---
+++
@@ -65,7 +65,7 @@
sage: dvdx = diff(v, x)-v -sign(x) == 0 -sage: desolve(de=dvdx, ivar=x, dvar=v"]) +sage: desolve(de=dvdx, ivar=x, dvar=v) sage: (c + integrate(e^(-x)sgn(x), x))e^x
There are several issues here, actually, so it may take a bit to solve this. We are apparently translating several things wrongly by not going through SR, but then there is also the 'general' variable ?g2733
which I remember being still undealt with... probably won't be fixed immediately :( just because of time constraints.
When trying to solve a simple ODE whose rhs contains a function, Sage fails to interpret the Maxima output if this contains integration limits.
A minimal example
if we now define a custom square pulse function
now we create a pulse function
and define differential equation
To get the evolution of v we can use desolve
The error message is:
desolve_laplace leads to similar error:
According to Nils Bruin, the problem is that Maxima 'at' function. As described in Ticket #385, this can be a problem with the implementation of 'at' for SR.
Expressions that work
And adding the sign function to the differential function does not affect the solution.
However, adding initial conditions produces an output that Sage is not able to evaluate
The output is:
I guess Sage is not able to interpret the integrations limits prompted by Maxima (e.g [t=0,v(t)=0]).
Detailed information (and a more realistic example) can be found here: http://groups.google.com/group/sage-support/browse_thread/thread/8cc67d39510faca2
CC: @kcrisman @nbruin
Component: calculus
Keywords: maxima, at, desolve
Issue created by migration from https://trac.sagemath.org/ticket/11653