Please help me in removing the error with explanation
Error on the following line:
_Sprite.position.x = _Body->GetPosition().x * _PhysicsWorld->RATIO;
Error message: Invalid operands to binary expression ('float32 (aka 'float') and 'float32()())
_Body is a B2Body object
_Sprite is a CCSprite object
_PhysicsWorld->RATIO returns float32
If I change the line to:
_Sprite.position.x = _Body->GetPosition().x * (float) _PhysicsWorld->RATIO;
Another error message comes: C-style cast from float32(*)() to float is not allowed.
You probably need to do:
_Sprite.position.x = _Body->GetPosition().x * _PhysicsWorld->RATIO();
Note the trailing '()' after RATIO.
You are multiplying a float (which parses into pointer dereferencing instead) by a function that returns a float (I believe).
Related
I have two 1-D of array of float ('Xdata' and 'tdata'). I want to make a new variable named 'ratedata'. The problem is when I run the code, the console showed "IndexError: only integers, slices (:), ellipsis (...), numpy.newaxis (None) and integer or boolean arrays are valid indices". How to encounter this problem? thank you.
the code:
dxdt_a = np.array(pd.read_excel('T50-katalis1-m14.xlsx',index_col=0,header=5))
Xdata = dxdt_a[:,1]
tdata = dxdt_a[:,0]
ratedata = np.zeros(len(Xdata))
for i in ratedata:
ratedata[i] = (Xdata[i+1]-Xdata[i])/(tdata[1]-tdata[0])
I am writing a Vpython simulation for projectile motion and keep getting the error ('float' object has no attribute '_x') on this line(ball.vel.y = ball.vel.y + g*dt) . I have tried changing the values of ball.vel.y to an integer and changing g to an integer but the same error occurs. Here is the code
from vpython import *
import math
ball=sphere(radius=0.1, color=color.red, pos=vector(0.1,0.1,0),make_trail=True)
floor=box(pos=vector(0,0,0), length=10, height=0.01, width=0.01)
g= vector(0,-9.8 ,0)
ball.vel=vector(10*cos(43),10*sin(43),0)
dt=0.1
t=0.0
while(ball.pos.y>-0.001):
rate(100)
t=t+dt
ball.pos.x = ball.pos.x + ball.vel.x*dt
ball.vel.y = ball.vel.y + g*dt
ball.pos.y = ball.pos.y + ball.vel.y*dt
g is a vector, as is g*dt, but ball.vel.y is a scalar, and you can't add a vector to a scalar. It's unfortunate that the error message doesn't just say "You can't add a vector to a scalar". I note that if you reverse the two quantities the error message is a bit more understandable: TypeError: unsupported operand type(s) for +: 'vpython.cyvector.vector' and 'float'
I made this function, but numba always give me error. Both chr_pos and pos are 1D arrays. What can be the problem?
#nb.njit
def create_needed_pos(chr_pos, pos):
needed_pos=[]
needed_pos=np.array(needed_pos,dtype=np.float64)
for i in range(len(chr_pos)):
for k in range(len(pos)):
if chr_pos[i] == pos[k]:
if i==1 and k==1:
needed_pos=pos[k]
else:
a=pos[k]
needed_pos=np.append(needed_pos,[a])
return needed_pos
needed_pos=create_needed_pos(chr_pos, pos)
The errors:
warnings.warn(errors.NumbaDeprecationWarning(msg,
<input>:1: NumbaWarning:
Compilation is falling back to object mode WITHOUT looplifting enabled because Function "create_needed_pos" failed type inference due to: Cannot unify array(float64, 1d, C) and int32 for 'needed_pos.1', defined at <input> (5)
File "<input>", line 5:
<source missing, REPL/exec in use?>
During: typing of intrinsic-call at <input> (9)
File "<input>", line 9:
<source missing, REPL/exec in use?>
The message
Cannot unify array(float64, 1d, C) and int32 for 'needed_pos.1'
is telling you that you are trying to assign an integer variable to an array. That happens in this line:
needed_pos=pos[k]
You can do that in normal Python, but Numba requires static types. You must assign an array of floats to an array of floats. For example, replacing the line by
needed_pos = pos[k:k+1]
The same error message says you are trying to assign an int, and this indicates that pos receives an array of ints. You must pass an array of floats instead.
After those changes, Numba still complains here:
needed_pos = []
needed_pos = np.array(needed_pos, dtype=np.float64)
with the message
numba.core.errors.TypingError: Failed in nopython mode pipeline (step: nopython frontend)
Cannot infer the type of variable 'needed_pos', have imprecise type: list(undefined)<iv=None>.
because it doesn't know the type of the elements that needed_pos will contain.
You can replace those two lines with one that creates an array of size zero with a known type:
needed_pos = np.array((0,), dtype=np.float64)
Now the program compiles and produces the same result with or without Numba.
But a problem remains. Numpy arrays work best when they have a fixed size. If you are continuously adding elements you'd better use lists (Numba lists in this case). This way for example:
#nb.njit
def create_needed_pos(chr_pos, pos):
needed_pos = nb.typed.List.empty_list(nb.float64)
for i in range(len(chr_pos)):
for k in range(len(pos)):
if chr_pos[i] == pos[k]:
if i == k == 1:
needed_pos = nb.typed.List([pos[k]])
else:
needed_pos.append(pos[k])
return needed_pos
This is my program-
#n= no. of days
def ATR(df , n):
df['H-L'] = abs(df['High'] - df['Low'])
df['H-PC'] = abs(df['High'] - df['Close'].shift(1))
df['L-PC'] = abs(df['Low'] - df['Close'].shift(1))
df['TR']=df[['H-L','H-PC','L-PC']].max(axis=1)
df['ATR'] = np.nan
df.ix[n-1,'ATR']=df['TR'][:n-1].mean()
for i in range(n , len(df)):
df['ATR'][i] = (df['ATR'][i-1]*(n-1) + df['TR'][i])/n
return
A warning shows up
'DataFrame' object has no attribute 'ix
I tried to replace it with iloc:
df.iloc[df.index[n-1],'ATR'] = df['TR'][:n-1].mean()
But this time another error pops up :
only integers, slices (`:`), ellipsis (`...`), numpy.newaxis (`None`) and integer or boolean arrays are valid indices
How to fix this?
Converting code is a pain and we have all been there...
df.ix[n-1,'ATR'] = df['TR'][:n-1].mean()
should become
df['ATR'].iloc[n-1] = df['TR'][:n-1].mean()
Hope this fits the bill
I am trying to code a java methods which returns a Boolean true if a point(x,y) is on a line segment and false if not.
I tried this:
public static boolean OnDistance(MyLocation a, MyLocation b, MyLocation queryPoint) {
double value = java.lang.Math.signum((a.mLongitude - b.mLongitude) * (queryPoint.mLatitude - a.mLatitude)
- (b.mLatitude - a.mLatitude) * (queryPoint.mLongitude - a.mLongitude));
double compare = 1;
if (value == compare) {
return true;
}
return false;
}
but it doesn't work.
I am not JAVA coder so I stick to math behind ... For starters let assume you are on plane (not sphere surface)
I would use Vector math so let:
a,b - be the line endpoints
q - queried point
c=q-a - queried line direction vector
d=b-a - line direction vector
use dot product for parameter extraction
t=dot(c,d)/(|c|*|d|)
t is line parameter <0,1> if out of range q is not inside line
|c|=sqrt(c.x*c.x+c.y*c.y) size of vector
dot(c,d)=c.x*d.x+c.y*d.y scalar vector multiply
now compute corresponding point on line
e=a+(t*d)
e is the closest point to q on the line ab
compute perpendicular distance of q and ab
l=|q-e|;
if (l>treshold) then q is not on line ab else it is on the line ab. The threshold is the max distance from line you are still accepting as inside line. No need to have l sqrt-ed the threshold constant can be powered by 2 instead for speed.
if you add all this to single equation
then some things will simplify itself (hope did not make some silly math mistake)
l=|(q-a)-(b-a)*(dot(q-a,b-a)/|b-a|^2)|;
return (l<=treshold);
or
l=|c-(d*dot(c,d)/|d|^2)|;
return (l<=treshold);
As you can see we do not even need sqrt for this :)
[Notes]
If you need spherical or ellipsoidal surface instead then you need to specify it closer which it is what are the semi axises. The line become arc/curve and need some corrections which depends on the shape of surface see
Projecting a point onto a path
but can be done also by approximation and may be also by binary search of point e see:
mine approx class in C++
The vector math used can be found here at the end:
Understanding 4x4 homogenous transform matrices
Here 3D C++ implementation (with different names):
double distance_point_axis(double *p,double *p0,double *dp)
{
int i;
double l,d,q[3];
for (i=0;i<3;i++) q[i]=p[i]-p0[i]; // q = p-p0
for (l=0.0,i=0;i<3;i++) l+=dp[i]*dp[i]; // l = |dp|^2
for (d=0.0,i=0;i<3;i++) d+=q[i]*dp[i]; // d = dot(q,dp)
if (l<1e-10) d=0.0; else d/=l; // d = dot(q,dp)/|dp|^2
for (i=0;i<3;i++) q[i]-=dp[i]*d; // q=q-dp*dot(q,dp)/|dp|^2
for (l=0.0,i=0;i<3;i++) l+=q[i]*q[i]; l=sqrt(l); // l = |q|
return l;
}
Where p0[3] is any point on axis and dp[3] is direction vector of axis. The p[3] is the queried point you want the distance to axis for.