Importing complex numbers into mathematica

[mike]

Hi

This may be a stupid question but is there an easy way to import
complex numbers from a file into mathematica. I have written some c++
code that outputs a set of complex numbers to a file and I have been
trying to get them into mathematica. What format should I use?

To give myself a clue I exported a couple of complex numbers from
Mathematica to see what the file would look like:

Export["test.dat", {3 + 2 I, 1 + 0.5 I}, "List"];

which gives me the following test.dat:
3 + 2 I
1 + 0.5 I

so far so good - looks like thats the format I need my c++ code to
output but when i try

test = Import["test.dat", "List"];
i get the following output
test = {3, "+", 2, "I", 1, "+", 0.5, "I"}

Can anyone help me? I want to be able to Import the file directly - I
would rather not simply import a big list of numbers and write a
function that makes the relavent ones complex. Any help would be much
appreciated

Mike

[Dale Horton]

The separation between list elements is determined by a ConversionOption

Import["test.dat", "List",
ConversionOptions -> {"ListSeparators" -> {"\n", "\r"}}]

-Dale

[Sseziwa Mukasa]

On Thursday, October 31, 2002, at 04:41 AM, mike wrote:

> Hi
>
> This may be a stupid question but is there an easy way to import
> complex numbers from a file into mathematica. I have written some c++
> code that outputs a set of complex numbers to a file and I have been
> trying to get them into mathematica. What format should I use?
>
> To give myself a clue I exported a couple of complex numbers from
> Mathematica to see what the file would look like:
>
> Export["test.dat", {3 + 2 I, 1 + 0.5 I}, "List"];
>
> which gives me the following test.dat:
> 3 + 2 I
> 1 + 0.5 I
>
> so far so good - looks like thats the format I need my c++ code to
> output but when i try
>
> test = Import["test.dat", "List"];
> i get the following output
> test = {3, "+", 2, "I", 1, "+", 0.5, "I"}
>
> Can anyone help me? I want to be able to Import the file directly - I
> would rather not simply import a big list of numbers and write a
> function that makes the relavent ones complex. Any help would be much
> appreciated
>

If you are only going to read the file in Mathematica output the
results as a Mathematica expression e.g. {3+2 I, 1+0.5 I} and use << to
read it in Mathematica.

Regards,

Ssezi

[Tomas Garza]

One possibility is that you keep your source data as a "CSV" file. For
example,

In[1]:=
Export["test.dat", {3 + 2*I, 1 + 0.5*I}, "CSV"];

In[2]:=
test = Import["test.dat", "CSV"]
Out[2]=
{{"3 + 2*I", "1 + 0.5*I"}}

As you can see, the imported data are strings. Then use ToExpression to
convert them to numbers:

In[3]:=
a = ToExpression[test]
Out[3]=
{{3 + 2*I, 1 + 0.5*I}}

In[4]:=
Head[a[[1,1]]]
Out[4]=
Complex

I guess this is what you were looking for.

Tomas Garza
Mexico City

----- Original Message -----
From: "mike" <mike_u...@yahoo.co.uk>
Subject: Importing complex numbers into mathematica

> Hi
>
> This may be a stupid question but is there an easy way to import
> complex numbers from a file into mathematica. I have written some c++
> code that outputs a set of complex numbers to a file and I have been
> trying to get them into mathematica. What format should I use?
>
> To give myself a clue I exported a couple of complex numbers from
> Mathematica to see what the file would look like:
>
> Export["test.dat", {3 + 2 I, 1 + 0.5 I}, "List"];
>
> which gives me the following test.dat:
> 3 + 2 I
> 1 + 0.5 I
>
> so far so good - looks like thats the format I need my c++ code to
> output but when i try
>
> test = Import["test.dat", "List"];
> i get the following output
> test = {3, "+", 2, "I", 1, "+", 0.5, "I"}
>
> Can anyone help me? I want to be able to Import the file directly - I
> would rather not simply import a big list of numbers and write a
> function that makes the relavent ones complex. Any help would be much
> appreciated
>

> Mike
>
>

[Liguo Song]

Hi, Mike,

Using Export["Test.dat", {3 + 2 I, 1 + 0.5 I}, "Expression"] will get you the
file with the following content:

{3 + 2*I, 1 + 0.5*I}

Then, use Import["Test.dat","Expression"] will get {3+2 I, 1+0.5 I}. So, try to
make your program out in this format and then import as Expression.

Hope it helps.

Liguo

[Jens-Peer Kuska]

Hi,

and

ReadList["test.dat"]

does what you want.

Regards
Jens