Creating a Histogram with Data from a File.dat in MATLAB

[quasarLie]

Hello everyone, I'm trying to make a MATLAB program which read a file.dat and then do a histogram
This what I did

Data2=importdata('Ma.DAT');
R1=Data2.data(:,17)
R1(R1>-9.9)
L = 0:0.1:8;
histc(R1,L)
bar(L,histc(R1,L),'histc')
xlabel('R1')
ylabel('counts')

[FONT=PT Sans, san-serif]I want to eliminate all the number = -9.9 present in my clomn (R1), How can i do that? i tried this R1(R1>-9.9) but it doesn't work :p can anyone help me please?
Thanks

 

[olivermsun]

I want to eliminate all the number = -9.9 present in my clomn (R1), How can i do that? i tried this R1(R1>-9.9) but it doesn't work :p can anyone help me please?
Thanks

Try

R1 = R1(R1>-9.9) % Assign the new, "fixed" data back to R1

or, if you want to preserve the column indices,

R1(R1>-9.9) = NaN % These shouldn't appear in the histogram

 

[quasarLie]

Tnanks, the first one works, but the second one gives only value = -9.9 and Nan

 

[olivermsun]

Tnanks, the first one works, but the second one gives only value = -9.9 and Nan

Sorry, I meant R1(R1==-9.9)=NaN.

 

[quasarLie]

Thanks, the code doesn't give me the right x value et y value, do you have any idea why?

 

[olivermsun]

If you eliminate the R1 values that don't fit your criteria, but not the corresponding L values, then they won't line up.

If you have a picture or a more detailed description, that might help us understand the output you're getting.

 

[quasarLie]

It give me this histogram, which is not correct because i have 240 objects and B1 have value between 0 and 3.8 (by 0.1 step). and it should not be empty at the value=0.4

 

[olivermsun]

Are you sure your data have values in the interval [0.4, 0.5)?

 

[quasarLie]

Yes, these are my data
0.70 0.10 0 0.80 0.80 1 0.80 1.2 0.60 2.50 0 0.5 0.70 0.60 0.10 0.60 0.70 0.60 0.10 0.20 0.70 3.1 0.40 0.3
0.500000000000000
0.800000000000000
0.100000000000000
0.200000000000000
1.50000000000000
0.800000000000000
1.60000000000000
0.200000000000000
1
1
0.200000000000000
0.900000000000000
0.300000000000000
0
0.600000000000000
0.400000000000000
0.100000000000000
1.10000000000000
0.600000000000000
1
0.200000000000000
0.200000000000000
0.100000000000000
0.700000000000000
1.40000000000000
1.40000000000000
1.10000000000000
0.400000000000000
0.900000000000000
0.600000000000000
1.80000000000000
0.100000000000000
0.900000000000000
1.10000000000000
0.700000000000000
0.300000000000000
0.400000000000000
2.90000000000000
0.300000000000000
0.300000000000000
0.600000000000000
1.30000000000000
0.600000000000000
1.50000000000000
0.100000000000000
0.100000000000000
0.600000000000000
1.60000000000000
0.200000000000000
1.50000000000000
0.200000000000000
0.600000000000000
0.300000000000000
1.10000000000000
0.500000000000000
0
1
0.400000000000000
0.400000000000000
4
0.200000000000000
0.100000000000000
0.900000000000000
0.700000000000000
0.800000000000000
0.500000000000000
0.300000000000000
0.700000000000000
0.300000000000000
0.900000000000000
1
0.900000000000000
0.600000000000000
0.600000000000000
2.50000000000000
0.600000000000000
0.400000000000000
0.100000000000000
0.800000000000000
2.30000000000000
0.900000000000000
0.200000000000000
0
0.200000000000000
0.500000000000000
3
1.20000000000000
7.50000000000000
1.30000000000000
0.300000000000000
0
1
1.70000000000000
0.400000000000000
1.50000000000000
0.700000000000000
0.200000000000000
0.400000000000000
0.400000000000000
0.100000000000000
0.100000000000000
0.800000000000000
3.70000000000000
3.40000000000000
0.300000000000000
0.100000000000000
0.400000000000000
0
1.20000000000000
0
0.800000000000000
0.100000000000000
0.100000000000000
0.100000000000000
0.300000000000000
0.500000000000000
1.40000000000000
0.400000000000000
0.400000000000000
0.400000000000000
0.100000000000000
1.10000000000000
0.400000000000000
0.400000000000000
0
0.100000000000000
0.300000000000000
0.700000000000000
0.500000000000000

 

[olivermsun]

The unexpected behavior comes from your use of the : operator to make your array of bin edges, in the statement:

L = 0:0.1:8;

There is a small floating point error in the bin edges that causes data points such as 0.300000000000000, which lie (almost) exactly at the edge between two bins, to be inconsistently included into one (intended) bin as opposed to the next.

To illustrate what is happening, try the following code:

a = L - 0.3;
a(4)

 

[quasarLie]

Soory but i really don't see how i can fix it. I tried what you said but it changes nothing iot gives the same histogram

 

[quasarLie]

Are you sure your data have values in the interval [0.4, 0.5)?

The unexpected behavior comes from your use of the : operator to make your array of bin edges, in the statement:

L = 0:0.1:8;

There is a small floating point error in the bin edges that causes data points such as 0.300000000000000, which lie (almost) exactly at the edge between two bins, to be inconsistently included into one (intended) bin as opposed to the next.

To illustrate what is happening, try the following code:

a = L - 0.3;
a(4)

what do you mean by between two bins, why this happens only with 0.3 and 0.7??

 

[olivermsun]

You are using histc() to break up the data into bins, with the border between bins at 0.0, 0.1, 0.2, ..., right?
How does it decide where to put the data point 0.300000000000000?