Problem with numbering theorem by section

Question

I am having a problem with the numbering of the theorems (by section) in a paper. My problem is that I want to number my theorems and propositions such that they appear as something like:

Theorem 3.1, Proposition 3.1 etc.

However, using the current list of commands I have, I am getting the following:

Theorem 31, Proposition 31 etc.

It seems like at least for the theorem command that I have put in, it is the usual command to call when trying to number theorems by section, so I am a little stumped why I am getting this error.

Here is my list of packages and commands:

documentclass[smallextended,referee]{svjour3}

smartqed

usepackage{graphicx}
usepackage{epstopdf}% To incorporate .eps illustrations using PDFLaTeX, etc.
usepackage{subfigure}% Support for small, `sub' figures and tables
usepackage{amsmath}
usepackage{amssymb}
usepackage{amscd}
usepackage{epsfig}
usepackage{amsfonts}
usepackage{amsthm}
usepackage{color}

theoremstyle{plain}
newtheorem{thm}{Theorem}[section]
newtheorem{cor}[theorem]{Corollary}
newtheorem{lem}[theorem]{Lemma}
newtheorem{ntn}{Notations}[section]
newtheorem{pro}{Proposition}[section]
newtheorem{dfn}{Definition}[section]
newtheorem{as}{Assumption}[section]
newtheorem{rem}{Remark}[section]
newtheorem{ob}{Observation}[section]

renewcommand{thefigure}{arabic{section}.arabic{figure}}
renewcommand{theequation}{arabic{section}.arabic{equation}}
defdiv{mathop{rm div}}
defD{mathop{bf rm D}}
defFP{mathop{rm p}}
defSpan{mathop{rm Span}}
defboldalpha{mbox{boldmath $alpha$}}
defboldpi{mbox{boldmath $pi$}}
defboldzeta{mbox{boldmath $zeta$}}
defboldtheta{mbox{boldmath $theta$}}

begin{document}

section{Solution}label{Solution}

begin{lem}label{conditions}
 Words for lemma
end{lem}

begin{thm}label{mainthm}
 Words for theorem
end{thm}

begin{rem}label{remone}
Words for remark
end{rem}

section{Analysis}label{Analysis}

begin{pro}label{observation}
Words for proposition
end{pro}

begin{rem}label{remtwo}
Words for remark
end{rem}

begin{thm}label{secondthm}
Words for remark
end{thm}

begin{pro}label{proposition}
Words for proposition
end{pro}

end{document}

egreg · Accepted Answer

Theorem-like environments should be defined, with the svjour3 class, by using

spnewtheorem

and not newtheorem. Here's how you should do:

documentclass[smallextended,referee,envcountsect]{svjour3}

usepackage{amsmath}
usepackage{bm}

smartqed
journalname{foo}

% Theorem-like environments are defined with spnewtheorem
%
% Usage:
%
%     spnewtheorem{env_nam}{caption}[within]{cap_font}{body_font}
% or  spnewtheorem{env_nam}[numbered_like]{caption}{cap_font}{body_font}
% or  spnewtheorem*{env_nam}{caption}{cap_font}{body_font}

spnewtheorem{thm}{Theorem}[section]{bfseries}{itshape}
spnewtheorem{cor}[theorem]{Corollary}{bfseries}{itshape}
spnewtheorem{lem}[theorem]{Lemma}{bfseries}{itshape}
spnewtheorem{ntn}{Notations}[section]{bfseries}{itshape}
spnewtheorem{pro}{Proposition}[section]{bfseries}{itshape}
spnewtheorem{dfn}{Definition}[section]{bfseries}{itshape}% maybe upshape?
spnewtheorem{as}{Assumption}[section]{bfseries}{itshape}
spnewtheorem{rem}{Remark}[section]{bfseries}{itshape}
spnewtheorem{ob}{Observation}[section]{bfseries}{itshape}

DeclareMathOperator{Div}{div} % div is already defined
DeclareMathOperator{D}{mathbf{D}}
DeclareMathOperator{FP}{p}
DeclareMathOperator{Span}{Span}

newcommand{boldalpha}{bm{alpha}}
newcommand{boldpi}{bm{pi}}
newcommand{boldzeta}{bm{zeta}}
newcommandboldtheta{bm{theta}}

begin{document}

section{Solution}label{Solution}

begin{lem}label{conditions}
 Words for lemma
end{lem}

begin{thm}label{mainthm}
 Words for theorem
end{thm}

begin{rem}label{remone}
Words for remark
end{rem}

section{Analysis}label{Analysis}

begin{pro}label{observation}
Words for proposition
end{pro}

begin{rem}label{remtwo}
Words for remark
end{rem}

begin{thm}label{secondthm}
Words for remark
end{thm}

begin{pro}label{proposition}
Words for proposition
end{pro}

end{document}

Note that I left only the packages necessary for the example to run. Note also how I redefined your personal commands, in the correct way: in particular, don't redefine commands you don't know about (div, in this case).

About the packages you load in the example:

amsfonts is already loaded by amssymb
amsthm is not compatible with svjour3
epsfig must not be loaded in new document (it's just for back compatibility)
subfigure has been obsolete for 10+ years, call

usepackage[caption=false]{subfig}

instead; the subfigure command becomes subfloat.

About the theorem numbering: having separate counters for all kinds of statements is unnecessarily confusing for the reader, who will have hard times in finding the statements when referenced at: is lemma 1.1 before or after proposition 1.1?

LanternD · Answer

Actually I have tried the solution of egreg's, and then find out that you don't need to create the command spnewtheorem{xx}{XX}[section]

It is the option  envcountsect in the svjour3 class that really helps.

documentclass[envcountsect]{svjour3}

If you look into the file svjour.cls, and seach spnewtheorem{theorem}{Theorem}, around line 888, you would find things like @envcntsect is prerequisite of the numbering by section.

And then, you just use

begin{theorem}
    your theorem here.
end{theorem}

to wrap your theorem. Proof, lemma, definition, case... are likewise.

user223793 · Answer

You should use  documentclass[natbib,smallextended, envcountsect]{svjour3}

Problem with numbering theorem by section

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