So if I am getting this correctly, since I want to plot this function, I need several values therefor I need to multiply them on an element by element basis ? Is this correct ?
The exponential and sinusoid terms you are multiplying are both vectors of dimension 1 x length(t). Your original code tried to multiply them, but to multiply two matrices, their inner dimension must agree. For example, if A is (mxn) and B is (nxp), A*B is of dimension (mxn)*(nxp), or (mxp). B*A is not defined, as that would result in (nxp)*(mxn), and the inner dimensions don't "cancel" each other.
In this case, length(t) is 1001. You originally tried to multiply (examining the dimension only) (1x1001)*(1x1001). If you look at the inner two dimensions, i.e., 1001)*(1, they are of different sizes. What you were really tring to do is to multiply the magnitudes of the two terms evaluated at each individual point in vector t (i.e., perform element by element multiplication, as tompouce indicated), not multiply the two vectors. This will result in an answer that is 1x1001 in dimension, which can then be plotted against t, since to plot, the lengths of the two vectors must also be equal.
xnuke
Please see FAQ731-376 for tips on how to make the best use of Eng-Tips.
as you're only working on the same function calculated at different times, you need to do an element by element multiplication (in opposition to on a single calculation using matrix arguments)
Tom
Red Flag Submitted
Thank you for helping keep Eng-Tips Forums free from inappropriate posts. The Eng-Tips staff will check this out and take appropriate action.
Reply To This Thread
Posting in the Eng-Tips forums is a member-only feature.
Learn methods and guidelines for using stereolithography (SLA) 3D printed molds in the injection molding process to lower costs and lead time. Discover how this hybrid manufacturing process enables on-demand mold fabrication to quickly produce small batches of thermoplastic parts. Download Now
Examine how the principles of DfAM upend many of the long-standing rules around manufacturability - allowing engineers and designers to place a part’s function at the center of their design considerations. Download Now
Metal 3D printing has rapidly emerged as a key technology in modern design and manufacturing, so it’s critical educational institutions include it in their curricula to avoid leaving students at a disadvantage as they enter the workforce. Download Now
This ebook covers tips for creating and managing workflows, security best practices and protection of intellectual property, Cloud vs. on-premise software solutions, CAD file management, compliance, and more. Download Now
RE: simple problem for experienced user
CODE
0.206*exp((-3.747*t)).*sin(15.36*t)
RE: simple problem for experienced user
I knew it was simple ... I never was familiar with the ".*" operator.
Thanks for the quick reply
-R
RE: simple problem for experienced user
what your first line does is multiply 2 line vectors using the matrix multiplication.
As what you want is to do element-by-element multiplication, you have to use the ".*" operator where necessary:
CODE
quicker than me, jisb
RE: simple problem for experienced user
So if I am getting this correctly, since I want to plot this function, I need several values therefor I need to multiply them on an element by element basis ? Is this correct ?
RE: simple problem for experienced user
In this case, length(t) is 1001. You originally tried to multiply (examining the dimension only) (1x1001)*(1x1001). If you look at the inner two dimensions, i.e., 1001)*(1, they are of different sizes. What you were really tring to do is to multiply the magnitudes of the two terms evaluated at each individual point in vector t (i.e., perform element by element multiplication, as tompouce indicated), not multiply the two vectors. This will result in an answer that is 1x1001 in dimension, which can then be plotted against t, since to plot, the lengths of the two vectors must also be equal.
xnuke
Please see FAQ731-376 for tips on how to make the best use of Eng-Tips.
RE: simple problem for experienced user
as you're only working on the same function calculated at different times, you need to do an element by element multiplication (in opposition to on a single calculation using matrix arguments)
Tom