Why do I get "ufunc 'multiply' did not contain a loop with signature matching types dtype('S32') dtype('S32') dtype('S32')" with values from raw_input
Question:
I am trying to create a really simple program that will plot a plot a parabola where v is velocity, a is acceleration and x is time. The user will input values for v and a, then v and a and x will determine y.
I attempted to do this with this:
x = np.linspace(0., 9., 10)
a = raw_input('Acceleration =')
v = raw_input('Velocity = ')
y = v * x - 0.5 * a * x**2.
But, I keep getting this error:
TypeError: ufunc ‘multiply’ did not contain a loop with signature matching types dtype(‘S32’) dtype(‘S32’) dtype(‘S32’)
What does this mean?
Answers:
From the documentation of raw_input:
The function then reads a line from input, converts it to a string (stripping a trailing newline), and returns that.
So what happens is that you try to multiply a string with a float, something like y="3" * x - 0.5 * "3" *x**2, which is not defined.
The easiest way to circumvent this is to cast the input string to float first.
x = np.linspace(0., 9., 10)
a = float(raw_input('Acceleration ='))
v = float(raw_input('Velocity = '))
y = v * x - 0.5 * a * x**2
Mind that if you’re using Python 3, you’d need to use input instead of raw_input,
a = float(input('Acceleration ='))
I faced this problem recently, change the dtype of x to something specific by doing:
x = np.asarray(x, dtype='float64')
I am trying to create a really simple program that will plot a plot a parabola where v is velocity, a is acceleration and x is time. The user will input values for v and a, then v and a and x will determine y.
I attempted to do this with this:
x = np.linspace(0., 9., 10)
a = raw_input('Acceleration =')
v = raw_input('Velocity = ')
y = v * x - 0.5 * a * x**2.
But, I keep getting this error:
TypeError: ufunc ‘multiply’ did not contain a loop with signature matching types dtype(‘S32’) dtype(‘S32’) dtype(‘S32’)
What does this mean?
From the documentation of raw_input:
The function then reads a line from input, converts it to a string (stripping a trailing newline), and returns that.
So what happens is that you try to multiply a string with a float, something like y="3" * x - 0.5 * "3" *x**2, which is not defined.
The easiest way to circumvent this is to cast the input string to float first.
x = np.linspace(0., 9., 10)
a = float(raw_input('Acceleration ='))
v = float(raw_input('Velocity = '))
y = v * x - 0.5 * a * x**2
Mind that if you’re using Python 3, you’d need to use input instead of raw_input,
a = float(input('Acceleration ='))
I faced this problem recently, change the dtype of x to something specific by doing:
x = np.asarray(x, dtype='float64')