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[?] Plot probability distribution?

Alex Token
Posted 8 years ago

Hi All. I have an issue with plotting. The following data shows the probability distribution of a random variable X (here 25/81, 30/81 etc are the probabilities):

data={{1,25?81},{2,30?81},{4,19?81},{8,6?81},{16,1?81}}

I would like to plot a bar-chart like in the image below. However, using for example, Histogram[WeightedData @@ Transpose[data], Length[data]] command I get a plot which is different. I would like the one where the bars are spaced like in the image below. I appreciate your help.

enter image description here
POSTED BY: Alex Token
10 Replies
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Alex Token
Alex Token
Posted 8 years ago

Thank you very much Valeriu. It worked well, have a nice day.
POSTED BY: Alex Token

Yes, I think so. I have done a simple modification in the code which must exclude the trouble. Try this:

data = {{1, 25/81}, {2, 30/81}, {4, 19/81}, {8, 6/81}, {16, 1/81}};
len = Length[data];
data1 = {Range[data[[1, 1]], data[[len, 1]]], Table[0, data[[len, 1]]]};
Do[data1[[2, data[[i, 1]]]] = data[[i, 2]], {i, len}];
BarChart[data1[[2]], ChartLabels -> data1[[1]], Frame -> True, GridLines -> {None, Automatic}]
POSTED BY: Valeriu Ungureanu
Alex Token
Alex Token
Posted 8 years ago

Dear Valeriu. Thank you. But I again receive the following error:

During evaluation of In[1]:= Table::itform: Argument data[[len,1]] at position 2 does not have the correct form for an iterator. >>

During evaluation of In[1]:= Table::itform: Argument data[[len,1]] at position 2 does not have the correct form for an iterator. >>

During evaluation of In[1]:= Set::partw: Part 4 of Table[25/81,10/27] does not exist. >>

During evaluation of In[1]:= Set::partw: Part 8 of Table[25/81,10/27] does not exist. >>

During evaluation of In[1]:= Set::partw: Part 16 of Table[25/81,10/27] does not exist. >>

During evaluation of In[1]:= General::stop: Further output of Set::partw will be suppressed during this calculation. >>

During evaluation of In[1]:= Table::itform: Argument 10/27 at position 2 does not have the correct form for an iterator. >>

During evaluation of In[1]:= BarChart::ldata: Table[25/81,10/27] is not a valid dataset or list of datasets. >>

During evaluation of In[1]:= BarChart::ldata: Table[25/81,10/27] is not a valid dataset or list of datasets. >>

During evaluation of In[1]:= BarChart::ldata: Table[25/81,10/27] is not a valid dataset or list of datasets. >>

During evaluation of In[1]:= General::stop: Further output of BarChart::ldata will be suppressed during this calculation. >>

Out[5]= BarChart[Table[25/81, 10/27], ChartLabels -> {1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16}, Frame -> True, GridLines -> {None, Automatic}]
POSTED BY: Alex Token

Dear Alex,

I have found the source of the error in the Mathematica 10. Table[0, data[[Length[data], 1]]] must have an iterator form Table[0, {i, data[[Length[data], 1]]}]. So, the following code works perfectly in Mma 10:

data = {{1, 25/81}, {2, 30/81}, {4, 19/81}, {8, 6/81}, {16, 1/81}};
data1 = {Range[data[[1, 1]], data[[Length[data], 1]]], 
   Table[0, {i, data[[Length[data], 1]]}]};
Do[data1[[2, data[[i, 1]]]] = data[[i, 2]], {i, Length[data]}];
BarChart[data1[[2]], ChartLabels -> data1[[1]], Frame -> True, 
 GridLines -> {None, Automatic}]
POSTED BY: Valeriu Ungureanu

Dear Alex,

I have executed the code from your file. The result you can see below:

enter image description here

What is the version of your Wolfram Mathematica?

POSTED BY: Valeriu Ungureanu
Alex Token
Alex Token
Posted 8 years ago

Dear Valeriu. I am using Wolfram 10.0. Maybe this is the issue? Thank you.
POSTED BY: Alex Token
Alex Token
Alex Token
Posted 8 years ago

Thank you for your reply. I copied and pasted the code but it does not produce the same outcome as in yours. I attach here a mat file. Thank you.

Attachments:
POSTED BY: Alex Token

Does the following code satisfy your desire?

data = {{1, 25/81}, {2, 30/81}, {4, 19/81}, {8, 6/81}, {16, 1/81}};
data1 = {Range[data[[1, 1]], data[[Length[data], 1]]], 
   Table[0, data[[Length[data], 1]]]};
Do[data1[[2, data[[i, 1]]]] = data[[i, 2]], {i, Length[data]}];
BarChart[data1[[2]], ChartLabels -> data1[[1]], Frame -> True, 
 GridLines -> {None, Automatic}]

enter image description here
POSTED BY: Valeriu Ungureanu
Alex Token
Alex Token
Posted 8 years ago

Thank you very much for your help. I also noticed the numbers on the horizontal axis are evenly spaced between each other. This is the issue in my plot. Realistically, the distance between “8” and “16” is not the same as the distance between “1” and “2”. Is it possible to “correct” the axis to take care of this? Thank you.
POSTED BY: Alex Token

Use BarChart:

data={{1,25/81},{2,30/81},{4,19/81},{8,6/81},{16,1/81}}
BarChart[data[[All,2]],ChartLabels->data[[All,1]],Frame->True,GridLines->{None,Automatic}]

You can fine-tune the axes, legend, gridlines and so on…
POSTED BY: Sander Huisman
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