I had a set of data and I plot it as in Figure 1
Then I used the lowpass filter to remove noise as below
N = length(FM);
n = floor(0.005*N);
H = zeros(size(FM));
H(1:n) = 1;
H( (N/2+2):N ) = H(N/2:-1:2);
LP_FM = FM .* H;
lp_fm = ifft(LP_FM);
plot(timesec,fm);
hold on
plot(timesec,real(lp_fm),'Linewidth',2);
I got the results as in Figure 2
Could anyone tell me what I am doing wrong here, please?
Why I got the abnormal values at the beginning?
Greatly appreciate for your help :)
Thanks!
Related
In the code supplied below I am trying to iterate over 2D numpy array [i][k]
Originally it is a code which was written in Fortran 77 which is older than my grandfather. I am trying to adapt it to python.
(for people interested whatabouts: it is a simple hydraulics transients event solver)
Bear in mind that all variables are introduced in my code which I don't paste here.
H = np.zeros((NS,50))
Q = np.zeros((NS,50))
Here I am assigning the first row values:
for i in range(NS):
H[0][i] = HR-i*R*Q0**2
Q[0][i] = Q0
CVP = .5*Q0**2/H[N]
T = 0
k = 0
TAU = 1
#Interior points:
HP = np.zeros((NS,50))
QP = np.zeros((NS,50))
while T<=Tmax:
T += dt
k += 1
for i in range(1,N):
CP = H[k][i-1]+Q[k][i-1]*(B-R*abs(Q[k][i-1]))
CM = H[k][i+1]-Q[k][i+1]*(B-R*abs(Q[k][i+1]))
HP[k][i-1] = 0.5*(CP+CM)
QP[k][i-1] = (HP[k][i-1]-CM)/B
#Boundary Conditions:
HP[k][0] = HR
QP[k][0] = Q[k][1]+(HP[k][0]-H[k][1]-R*Q[k][1]*abs(Q[k][1]))/B
if T == Tc:
TAU = 0
CV = 0
else:
TAU = (1.-T/Tc)**Em
CV = CVP*TAU**2
CP = H[k][N-1]+Q[k][N-1]*(B-R*abs(Q[k][N-1]))
QP[k][N] = -CV*B+np.sqrt(CV**2*(B**2)+2*CV*CP)
HP[k][N] = CP-B*QP[k][N]
for i in range(NS):
H[k][i] = HP[k][i]
Q[k][i] = QP[k][i]
Remember i is for rows and k is for columns
What I am expecting is that for all k number of columns the values should be calculated until T<=Tmax condition is met. I cannot figure out what my mistake is, I am getting the following errors:
RuntimeWarning: divide by zero encountered in true_divide
CVP = .5*Q0**2/H[N]
RuntimeWarning: invalid value encountered in multiply
QP[N][k] = -CV*B+np.sqrt(CV**2*(B**2)+2*CV*CP)
QP[N][k] = -CV*B+np.sqrt(CV**2*(B**2)+2*CV*CP)
ValueError: setting an array element with a sequence.
Looking at your first iteration:
H = np.zeros((NS,50))
Q = np.zeros((NS,50))
for i in range(NS):
H[0][i] = HR-i*R*Q0**2
Q[0][i] = Q0
The shape of H is (NS,50), but when you iterate over a range(NS) you apply that index to the 2nd dimension. Why? Shouldn't it apply to the dimension with size NS?
In numpy arrays have 'C' order by default. Last dimension is inner most. They can have a F (fortran) order, but let's not go there. Thinking of the 2d array as a table, we typically talk of rows and columns, though they don't have a formal definition in numpy.
Lets assume you want to set the first column to these values:
for i in range(NS):
H[i, 0] = HR - i*R*Q0**2
Q[i, 0] = Q0
But we can do the assignment whole rows or columns at a time. I believe new versions of Fortran also have these 'whole-array' functions.
Q[:, 0] = Q0
H[:, 0] = HR - np.arange(NS) * R * Q0**2
One point of caution when translating to Python. Indexing starts with 0; so does ranges and np.arange(...).
H[0][i] is functionally the same as H[0,i]. But when using slices you have to use the H[:,i] format.
I suspect your other iterations have similar problems, but I'll stop here for now.
Regarding the errors:
The first:
RuntimeWarning: divide by zero encountered in true_divide
CVP = .5*Q0**2/H[N]
You initialize H as zeros so it is normal that it complains of division by zero. Maybe you should add a conditional.
The third:
QP[N][k] = -CV*B+np.sqrt(CV**2*(B**2)+2*CV*CP)
ValueError: setting an array element with a sequence.
You define CVP = .5*Q0**2/H[N] and then CV = CVP*TAU**2 which is a sequence. And then you try to assign a derivate form it to QP[N][K] which is an element. You are trying to insert an array to a value.
For the second error I think it might be related to the third. If you could provide more information I would like to try to understand what happens.
Hope this has helped.
import random
l = "lava"
d = "dessert"
f = "forest"
v = "village"
s = "sect"
w = "water"
c = "city"
m = "mountains"
p = "plains"
t = "swamp"
map_list = [l,d,f,v,s,w,c,m,p,t]
map = []
for i in range(50):
map.append([])
def rdm_map(x):
for i in range(50):
map[x].append(random.choice(map_list))
def map_create():
x = 0
while x <= len(map):
rdm_map(x)
x + 1
map_create()
print(map[2][1])
I'm not getting anything for output not even an error code.I'm trying to create a randomly generated game map of descent size but when i went to run it nothing happened i'm thinking since my computer isn't that great its just taking way to long to process but i just wanted to post it on here to double check. If that is the issue is there a way to lessen the load without lessening the map size?
You have the following bugs:
Inside the map_create you must change x + 1 to x += 1. For this reason your script runs for ever.
After that you should change the while x <= len(map): to while x < len(map):. If you keep the previous, you will get a Index Error.
In any case, your code can be further improved. Please try to read some pages of the tutorial first.
I want to ask for any help to solve my problem. I want to compute BER (Bit error rate) for a nine combination points as illustrated below. I used the computation for SER and then I convert it to BER, but the result was incorrect. Any site or suggestion please?
Many thanks
Othman
My code is:
clear all clc
SNR = 0:40;
SNRL = 10.^(SNR./10);
Eb=1;
sigma = sqrt(2*Eb./SNRL);
d2 = 0.3;
Pe = 14/9*erfc((d2)./sqrt(2*sigma.^2))+2/9*erfc((0)./sqrt(2*sigma.^2));
semilogy(SNR,Pe) grid on hold on
I have a spreadsheet which works out margin price etc.
I'm wondering if I can reverse my Margin Calculator?
Presently it works out the Margin %
=((I1-F1)-H1-K1-N1)/I1
(I=Net Price, F=Cost, H=Carriage, K=Fees, N=Promotions)
I want to be able to type a Margin % and it calculates the price and if possible add the round up feature? so everything ends in .99.
Using
=ROUNDUP(SUM(I864*M864)+(I864),0.1)-0.01
(M being Margin field) it calculate using the margin, but it differs from the original price
e.g. Price 69.99=19% Margin
Reverse Calculation 19%=66.99
Difference of 3, i'm really confused and cannot get my head around this, can someone please shed some light?
If M1 = ((I1-F1)-H1-K1-N1)/I1 then reverse I1 = (F1+H1+K1+N1)/(1-M1).
This is done using math to change the subject of the formula:
M1 = ((I1-F1)-H1-K1-N1)/I1 / parenthesis not necessary
M1 = (I1-F1-H1-K1-N1)/I1 / multiply out brackets (*1/I1)
M1 = I1/I1 -F1/I1-H1/I1-K1/I1-N1/I1
M1 = 1 -F1/I1-H1/I1-K1/I1-N1/I1 / -1
M1-1 = -F1/I1-H1/I1-K1/I1-N1/I1 / *I1
(M1-1) * I1 = -F1-H1-K1-N1 / *-1
-1*(M1-1) * I1 = -1*(-F1-H1-K1-N1)
(1-M1) * I1 = F1+H1+K1+N1 / /(1-M1)
I1 = (F1+H1+K1+N1)/(1-M1)
I am trying to calculate a few hundred rows of data, solving a system of linear equations using matrices. I am building my matrices based on the row data. I take the inverse of the resultant 3x3 and then multiply twice, once for x's and once for y's. I get 6 variables from this: a,b,c,d,e and f. How can I copy down the example so that is solves for all rows? I am providing the data and then the formulas I am using now. Right now, if I copy down it skips 3 rows or if I copy down with 3 examples it skips 9 rows. I mean I guess I could go an try to insert extra rows into all 300 so I end up with 900 rows, but there has to be an easier way!
I can't figure out how to get my data to populate in here correctly so here is a link: http://codepad.org/qZwua3h9
Note: I split up the matrix rows so you could see them easier, they are not split up on my sheet.
Edit: If anyone can figure out how to paste the example data here I would welcome it so that this post may be of use to someone in the future. I am not sure how long codepad keeps their pastes.
I gave up and came to the conclusion that there is no reasonable amount of effort that will yield the desired results. Not only was the example case only ONE transformation, but the intended case was for 3 transformations - so three times the work. I came up with a Matlab solution in about 15 minutes. I understand that not everyone has access to Matlab though. So, if someone comes up with any reasonable working excel solution, I would welcome the knowledge and mark that answer as the accepted one. Regardless, here is the Matlab script:
M = csvread('pointData.csv');
T1result = zeros(215,6);
T2result = zeros(215,6);
T3result = zeros(215,6);
for i=1:215,
m = [M(i,1) M(i,2) 1; M(i,3) M(i,4) 1; M(i,5) M(i,6) 1];
x = [M(i,7);M(i,9);M(i,11)];
y = [M(i,8);M(i,10);M(i,12)];
xresult = m\x;
yresult = m\y;
T1result(i,:) = [transpose(xresult),transpose(yresult)];
m = [M(i,7) M(i,8) 1; M(i,9) M(i,10) 1; M(i,11) M(i,12) 1];
x = [M(i,13);M(i,15);M(i,17)];
y = [M(i,14);M(i,16);M(i,18)];
xresult = m\x;
yresult = m\y;
T2result(i,:) = [transpose(xresult),transpose(yresult)];
m = [M(i,13) M(i,14) 1; M(i,15) M(i,16) 1; M(i,17) M(i,18) 1];
x = [M(i,19);M(i,21);M(i,23)];
y = [M(i,20);M(i,22);M(i,24)];
xresult = m\x;
yresult = m\y;
T3result(i,:) = [transpose(xresult),transpose(yresult)];
end
LeafId = csvread('extraColumnsForID.csv');
Tresult = [LeafId, T1result, T2result, T3result];
csvwrite('transforms.csv',Tresult);