## Check result-condition number

For the discussion of math. Duh.

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evinda
Posts: 32
Joined: Fri May 03, 2013 10:16 pm UTC

### Check result-condition number

Hi!!
Could you tell me what is equal to the condition number of the matrix R,using the infinity norm, if R is a 50x50 tridiagonal matrix with the number 5 at the main diagonal and the number 6 at the first diagonal below this,and also the number 6 at the first diagonal above the main diagonal??
I found this result: 93.6551
Is this right??

NathanielJ
Posts: 882
Joined: Sun Jan 13, 2008 9:04 pm UTC

### Re: Check result-condition number

Yes. More specifically, it's 4885477064818389638136352610039211133217/52164587258011922567975512864675399397.
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evinda
Posts: 32
Joined: Fri May 03, 2013 10:16 pm UTC

### Re: Check result-condition number

Why is my result so different from yours????

Flumble
Yes Man
Posts: 2266
Joined: Sun Aug 05, 2012 9:35 pm UTC

### Re: Check result-condition number

evinda wrote:Why is my result so different from yours????

Did you not notice the little / in the middle?
The only difference is that you got ~5 digits of accuracy and Nathan got the exact result.

evinda
Posts: 32
Joined: Fri May 03, 2013 10:16 pm UTC

### Re: Check result-condition number

Flumble wrote:
evinda wrote:Why is my result so different from yours????

Did you not notice the little / in the middle?
The only difference is that you got ~5 digits of accuracy and Nathan got the exact result.

Oh sorry!!!!!!!I haven't noticed it before.

I have also an other question.Could you tell me which is the condition number,using the infinity norm,of the Hilbert matrix with n=400..
I found it: 3.1873e+021.I found it,by writing a code in matlab.When I run it I get the following warning:Matrix is close to singular or badly scaled.Results may be inaccurate.RCOND:3.137467e-022.

Ehat does this mean???Is my result wrong???

Cleverbeans
Posts: 1378
Joined: Wed Mar 26, 2008 1:16 pm UTC

### Re: Check result-condition number

evinda wrote:Ehat does this mean???Is my result wrong???

It means computers are not magic boxes that always give you an answer. They have limits and just like people when you give them larger problems they're more likely to make a mistake, and it is warning you about them.
"Labor is prior to, and independent of, capital. Capital is only the fruit of labor, and could never have existed if labor had not first existed. Labor is the superior of capital, and deserves much the higher consideration." - Abraham Lincoln

evinda
Posts: 32
Joined: Fri May 03, 2013 10:16 pm UTC

### Re: Check result-condition number

Cleverbeans wrote:
evinda wrote:Ehat does this mean???Is my result wrong???

It means computers are not magic boxes that always give you an answer. They have limits and just like people when you give them larger problems they're more likely to make a mistake, and it is warning you about them.

I understand..Thank you for your help

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